Direct fabrication of attachment templates with adhesive

ABSTRACT

Systems, methods, and devices for producing orthodontic appliances are provided. In one aspect, an orthodontic appliance comprises an outer shell comprising a plurality of cavities shaped to receive the patient&#39;s teeth and generate one or more of a force or a torque in response to the appliance being worn on the patient&#39;s teeth. The orthodontic appliance can comprise an inner structure having a stiffness different than a stiffness of the outer shell. The inner structure can be positioned on an inner surface of the outer shell in order to distribute the one or more of a force or a torque to at least one tooth received within the plurality of cavities.

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.15/202,348, filed Jul. 5, 2016, which claims the benefit of U.S.Provisional Application No. 62/189,282, filed Jul. 7, 2015, and U.S.Provisional Application No. 62/189,259, filed Jul. 7, 2015, thedisclosures of each of which are incorporated herein by reference intheir entirety.

The subject matter of the following co-pending patent applications isrelated to the present application: U.S. Application Ser. No.62/189,259, filed Jul. 5, 2016, entitled “MULTI-MATERIAL ALIGNERS”,which claims the benefit of U.S. Provisional Application No. 62/189,259,filed Jul. 7, 2015 and U.S. Provisional Application No. 62/189,282,filed Jul. 7, 2015; U.S. application Ser. No. 15/202,472, filed Jul. 5,2016, entitled “DIRECT FABRICATION OF ALIGNERS WITH INTERPROXIMAL FORCECOUPLING”, which claims the benefit of U.S. Provisional Application No.62/189,263, filed Jul. 7, 2015; U.S. application Ser. No. 15/202,452,filed Jul. 5, 2016, entitled “DIRECT FABRICATION OF ALIGNERS FOR ARCHEXPANSION”, which claims the benefit of U.S. Provisional Application No.62/189,271, filed Jul. 7, 2015, and U.S. Provisional Application No.62/189,301, filed Jul. 7, 2015; U.S. application Ser. No. 15/202,467,filed Jul. 5, 2016, entitled “DIRECT FABRICATION CROSS-LINKING FORPALATE EXPANSION AND OTHER APPLICATIONS”, which claims the benefit ofU.S. Provisional Application No. 62/189,301, filed Jul. 7, 2015, andU.S. Provisional Application No. 62/189,271, filed Jul. 7, 2015; U.S.application Ser. No. 15/202,254, filed Jul. 5, 2016, entitled “SYSTEMS,APPARATUSES AND METHODS FOR DENTAL APPLIANCES WITH INTEGRALLY FORMEDFEATURES”, which claims the benefit of U.S. Provisional Application No.62/189,291, filed Jul. 7, 2015, U.S. Provisional Application No.62/189,312, filed Jul. 7, 2015, and U.S. Provisional Application No.62/189,317, filed Jul. 7, 2015; U.S. application Ser. No. 15/202,299,filed Jul. 5, 2016, entitled “DIRECT FABRICATION OF POWER ARMS”, whichclaims the benefit of U.S. Provisional Application No. 62/189,291, filedJul. 7, 2015, U.S. Provisional Application No. 62/189,312, filed Jul. 7,2015, and U.S. Provisional Application No. 62/189,317, filed Jul. 7,2015; U.S. application Ser. No. 15/202,187, filed Jul. 5, 2016, entitled“DIRECT FABRICATION OF ORTHODONTIC APPLIANCES WITH VARIABLE PROPERTIES”,which claims the benefit of U.S. Provisional Application No. 62/189,291,filed Jul. 7, 2015, U.S. Provisional Application No. 62/189,312, filedJul. 7, 2015, and U.S. Provisional Application No. 62/189,317, filedJul. 7, 2015; U.S. application Ser. No. 15/202,139, filed Jul. 5, 2016,entitled “SYSTEMS, APPARATUSES AND METHODS FOR SUBSTANCE DELIVERY FROMDENTAL APPLIANCE”), which claims the benefit of U.S. ProvisionalApplication No. 62/189,303, filed Jul. 7, 2015; U.S. application Ser.No. 15/201,598, filed Jul. 5, 2016, entitled “DENTAL MATERIALS USINGTHERMOSET POLYMERS”, which claims the benefit of U.S. ProvisionalApplication No. 62/189,380, filed Jul. 7, 2015; and U.S. applicationSer. No. 15/202,083, filed Jul. 5, 2016, entitled “DENTAL APPLIANCEHAVING ORNAMENTAL DESIGN”, which claims the benefit of U.S. ProvisionalApplication No. 62/189,318, filed Jul. 7, 2015, the entire disclosuresof which are incorporated herein by reference.

BACKGROUND

Prior orthodontic procedures typically involve repositioning a patient'steeth to a desired arrangement in order to correct malocclusions and/orimprove aesthetics. To achieve these objectives, orthodontic appliancessuch as braces, retainers, shell aligners, and the like can be appliedto the patient's teeth by an orthodontic practitioner. The appliance canbe configured to exert force on one or more teeth in order to effectdesired tooth movements. The application of force can be periodicallyadjusted by the practitioner (e.g., by altering the appliance or usingdifferent types of appliances) in order to incrementally reposition theteeth to a desired arrangement.

Attachments can also be placed on teeth for dental and orthodontictreatments to aid in the repositioning of a patient's teeth.

The prior orthodontic methods and apparatus to move teeth can be lessthan ideal in at least some respects. In some instances priororthodontic approaches that employ an appliance with homogeneous and/orcontinuous material properties may not provide sufficient control overthe forces applied to the teeth. For example, prior appliancesfabricated from a single material may exhibit less than ideal controlover the forces applied to subsets of teeth. In some instances,relatively stiff orthodontic appliances may require tightermanufacturing tolerances than would be ideal, and the manufacturingtolerances may undesirably affect the accuracy of the applied forces inat least some instances. Also, in at least some instances the appliancemay distort at locations away from the teeth to be moved, such that theaccuracy of the tooth movement can be less than ideal.

Although attachment templates have been proposed to place attachments onteeth, the prior methods and apparatus can be somewhat more difficult touse than would be ideal. Also, the accuracy of the prior attachmenttemplates can be somewhat less accurate than would be ideal. The methodsof manufacture of the prior alignment templates can be somewhat moretime consuming and expensive than would be ideal.

In light of the above, improved orthodontic appliances are needed.Ideally such appliances would provide more accurate tooth movement withimproved control over the forces applied to the teeth, more constantamounts of force applied onto teeth during treatment, and reducedsensitivity to manufacturing tolerances.

SUMMARY

Improved systems, methods, and devices for repositioning a patient'steeth are provided herein. An orthodontic appliance for repositioningteeth comprises heterogeneous properties in order to improve control offorce and/or torque application onto different subsets of teeth. Forinstance, different portions of an appliance can comprise differentmaterial compositions in order to produce different localized stiffness,and the different localized stiffness can be used to generate localizedforces and/or torques that are customized to the particular underlyingteeth. In some embodiments, the appliance comprises a stiff outer shellthat generates the force and/or torque and a compliant inner structurethat engages with the tooth surface in order to improve the force and/ortorque distribution to the tooth. Advantageously, the use of a compliantinner structure coupled to a stiff outer shell can reduce fluctuationsin the amount of force or torque applied, which can improve the accuracyand reliability of the appliance. Alternatively or in combination, theapproaches described herein for appliance design and fabrication permitthe identification of spatial correspondences between portions of anappliance shell and portions of a material sheet used to form the shell,which can improve the accuracy of fabricating appliances with differentlocalized properties for improved control of the force and/or torqueapplication to teeth.

In a first aspect, an orthodontic appliance for repositioning apatient's teeth in accordance with a treatment plan comprises an outershell comprising a plurality of cavities shaped to receive the patient'steeth and generate one or more of a force or a torque in response to theappliance being worn on the patient's teeth. The orthodontic appliancecan comprise an inner structure having a stiffness different than astiffness of the outer shell. The inner structure can be positioned onan inner surface of the outer shell in order to distribute the one ormore of a force or a torque to at least one received tooth.

In another aspect, a method for designing an orthodontic appliance forrepositioning a patient's teeth in accordance with a treatment plancomprises receiving a 3D representation of a shell comprising aplurality of cavities shaped to receive the patient's teeth. The shellcan comprise a plurality of shell portions each positioned to engage adifferent subset of the patient's teeth. The method can further comprisegenerating a 2D representation corresponding to the 3D representation ofthe shell. The 2D representation can represent a material sheet to beused to form the shell. The material sheet can comprise a plurality ofsheet portions corresponding to the plurality of shell portions.

The methods and appliances disclosed herein also provide improvedplacement of attachments on teeth. The appliances can be directlymanufactured, such that the appliances can be manufactured in a costeffective manner. In many embodiments, the appliance comprises a supportcomprising one or more coupling structures to hold the one or moreattachments. An alignment structure is coupled to the support to receiveat least a portion of a tooth and positon the one or more attachments atone or more predetermined locations on the one or more teeth. The one ormore coupling structures are configured to release the attachment withremoval of the alignment structure from the one or more teeth. In someembodiments, an attachment can be directly manufactured with anadhesive, and a removable cover may be directly manufactured over theadhesive.

The one or more coupling structures can be directly manufactured andconfigured in many ways to release from the teeth. The one or morecoupling structures can be sized and shaped to hold the attachment. Theone or more coupling structures are sized and shaped to hold theattachment with a gap extending between the support and attachment. Theone or more coupling structures may comprise one or more extensionsextending between the support and the attachment. The one or morecoupling structures may comprise a plurality of extensions extendingbetween the support and the attachment. The one or more couplingstructures may comprise a separator sized and shaped to separate theattachment from the support. The one or more coupling structurescomprises a recess formed in the support, the recess sized and shaped toseparate the attachment from the support.

While the appliance can be manufactured in many ways, in manyembodiments the appliance is manufactured in response to threedimensional scan data of a mouth of the patient. Three dimensional scandata of a mouth of the patient can be received. A three dimensionalshape profile of a support determined in response to the threedimensional scan data, and a three dimensional shape profile of analignment structure is determined in response to the scan data. A threedimensional shape profile of the one or more coupling structures can bedetermined in response to the three dimensional scan data in order torelease the attachment with removal of the alignment structure from theone or more teeth.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1A illustrates a tooth repositioning appliance, in accordance withembodiments;

FIG. 1B illustrates a tooth repositioning system, in accordance withembodiments;

FIG. 2 illustrates a method of orthodontic treatment using a pluralityof appliances, in accordance with embodiments;

FIGS. 3A and 3B illustrate a portion of an orthodontic applianceincluding a stiff outer shell and a compliant inner structure, inaccordance with embodiments;

FIG. 3C illustrates a portion of a three-layer orthodontic appliance, inaccordance with embodiments;

FIG. 4A illustrates a cross-section of a three-layer orthodonticappliance with a stiff outer layer and a compliant inner layer, inaccordance with embodiments;

FIG. 4B illustrates a cross-section of an orthodontic appliance having acompliant inner layer with a thickened portion, in accordance withembodiments;

FIG. 4C illustrates a cross-section of an orthodontic applianceincluding a protrusion formed in the stiff outer layer, in accordancewith embodiments;

FIG. 4D illustrates a treatment system including a plurality of stiffouter shells to and a single compliant inner shell, in accordance withembodiments;

FIG. 5A illustrates an appliance with a plurality of discrete padstructures, in accordance with embodiments;

FIG. 5B illustrates an appliance with a plurality of discrete plugstructures, in accordance with embodiments;

FIG. 5C illustrates an appliance with a plurality of discrete inflatablestructures, in accordance with embodiments;

FIG. 5D illustrates an exemplary load-displacement curve for anappliance, in accordance with embodiments;

FIG. 5E illustrates an appliance with a plurality of discrete padstructures, in accordance with embodiments;

FIG. 5F illustrates an appliance with a plurality of connected padstructures, in accordance with embodiments;

FIG. 5G illustrates an appliance with a plurality of discrete padstructures, in accordance with embodiments;

FIG. 511 illustrates an appliance with a plurality of discrete padstructures, in accordance with embodiments;

FIG. 6A illustrates an appliance including an inner structure engaging atooth-mounted attachment, in accordance with embodiments;

FIG. 6B illustrates an appliance including a compliant tooth-mountedattachment, in accordance with embodiments;

FIG. 6C illustrates a compliant attachment-mounted structure with aprotective layer, in accordance with embodiments;

FIGS. 7A, 7B, and 7C schematically illustrate independent forceapplication on teeth, in accordance with embodiments;

FIG. 8A illustrates spatial correspondences between a patient's teeth,an orthodontic appliance, and a material sheet, in accordance withembodiments;

FIG. 8B illustrates a material sheet for forming an appliance, inaccordance with embodiments;

FIG. 8C illustrates a cross section of the material sheet of FIG. 8B, inaccordance with embodiments;

FIG. 8D illustrates a cross section of the material sheet of FIG. 8B, inaccordance with embodiments;

FIG. 9 illustrates a method for designing and fabricating an orthodonticappliance, in accordance with embodiments;

FIG. 10A illustrates an additive manufacturing process for fabricatingan appliance, in accordance with embodiments;

FIG. 10B illustrates a subtractive manufacturing process for fabricatingan appliance, in accordance with embodiments;

FIGS. 11A and 11B illustrate fabrication of a material sheet from aplurality of overlapping material layers, in accordance withembodiments;

FIGS. 12A through 12C illustrate fabrication of a material sheet from aplurality of non-overlapping material sections, in accordance withembodiments;

FIG. 13 illustrates a method for digitally planning an orthodontictreatment, in accordance with embodiments;

FIG. 14 is a simplified block diagram of a data processing system, inaccordance with embodiments;

FIG. 15 illustrates a method for designing an orthodontic appliance, inaccordance with embodiments.

FIG. 16 illustrates a method for designing an orthodontic appliance, inaccordance with embodiments;

FIG. 17A illustrates a directly fabricated attachment template, inaccordance with embodiments; and

FIG. 17B illustrates a detailed view of a receptacle of an attachmenttemplate, such as that illustrated in FIG. 17A.

DETAILED DESCRIPTION

Systems, methods, and devices for improved orthodontic treatment of apatient's teeth are provided herein. In some embodiments, the presentdisclosure provides improved orthodontic appliances having differentportions with different properties. The use of appliances with differentlocalized properties as described herein can improve control over theapplication of forces and/or torques to different subsets of teeth, thusenhancing the predictability and effectiveness of orthodontic treatment.For example, an orthodontic appliance can include portions withdifferent stiffness (e.g., a relatively stiff portion and a relativelycompliant portion) to provide more consistent force and/or torqueapplication even when manufacturing tolerances for the appliance arerelatively poor. Additionally, the appliance design and fabricationmethods described herein can enhance the accuracy and flexibility ofproducing appliances with different localized properties, thus allowingfor the production of more complex and customized appliances.

In one aspect, an orthodontic appliance for repositioning a patient'steeth in accordance with a treatment plan is provided. The appliance cancomprise an outer shell comprising a plurality of cavities shaped toreceive the patient's teeth and generate one or more of a force or atorque in response to the appliance being worn on the patient's teeth,and an inner structure having a stiffness different than a stiffness ofthe outer shell. The inner structure can be positioned on an innersurface of the outer shell in order to distribute the one or more of aforce or a torque to at least one tooth received within the plurality ofcavities.

In another aspect, an orthodontic appliance for repositioning apatient's teeth in accordance with a treatment plan is provided. Theappliance can comprise an outer shell comprising a plurality ofteeth-receiving cavities shaped to exert one or more of a force or atorque on the patient's teeth, and an inner structure positioned on aninner surface of the outer shell. The inner structure can comprise astiffness different than a stiffness of the outer shell such that theinner structure is configured to exhibit an amount of deformationgreater than an amount of deformation exhibited by the outer shell.

In some embodiments, the stiffness of the inner structure is less thanthe stiffness of the outer shell. The inner structure can be configuredto exhibit a first configuration prior to placement of the appliance onthe patient's teeth and a second configuration after the placement ofthe appliance on the patient's teeth. The first configuration can differfrom the second configuration with respect to one or more of: athickness profile of the inner structure, a cross-sectional shape of theinner structure, or an inner surface profile of the inner structure. Theinner structure can be configured to exhibit an amount of deformationgreater than an amount of deformation exhibited by the outer shell whenthe appliance is worn on the patient's teeth. The deformation of theinner structure can comprise one or more of: a change in a thicknessprofile of the inner structure, a change in a cross-sectional shape ofthe inner structure, or a change in an inner surface profile of theinner structure. The outer shell can exhibit substantially nodeformation when the appliance is worn on the patient's teeth.

In some embodiments, the inner structure comprises a compressiblematerial. The inner structure can have an elastic modulus within a rangefrom about 0.2 MPa to about 20 MPa.

In some embodiments, an inner surface profile of the outer shell differsfrom a surface profile of the at least one tooth so as to generate theone or more of a force or a torque when the appliance is worn on thepatient's teeth. For example, the inner surface profile of the outershell can comprise a position or an orientation of a tooth-receivingcavity different from a position or an orientation of the surfaceprofile of at least one tooth received within the tooth-receivingcavity. The inner surface profile of the outer shell can comprise aprotrusion extending inwards towards the at least one tooth, and whereinthe inner structure is positioned between the protrusion and the atleast one tooth.

In some embodiments, the inner structure comprises a continuous innerlayer positioned between the outer shell and the patient's teeth. Thecontinuous inner layer can be removably coupled to the outer shell orpermanently affixed to the outer shell. The continuous inner layer cancomprise a first layer portion with an increased thickness relative to asecond layer portion, and the first layer portion can be positioned toengage the at least one tooth in order to distribute one or more of aforce or a torque.

In some embodiments, the inner structure comprises one or more discretepad structures positioned to engage the at least one tooth. The one ormore discrete pad structures can engage the at least one received toothvia one or more attachments mounted on the at least one tooth.Optionally, the inner structure can comprise a plurality of discrete padstructures each positioned to engage a different portion of the at leastone tooth. The one or more discrete pad structures can be solid.Alternatively, the one or more discrete pad structures can be hollow. Insome embodiments, the one or more discrete pad structures are filledwith a fluid optionally maintained at a substantially constant pressure.

In some embodiments, the inner structure is coupled to the inner surfaceof the outer shell. Alternatively or in combination, the inner structurecan be coupled to a tooth surface or an attachment mounted on the toothsurface.

In some embodiments, the appliance further comprises an outermost layercoupled to an outer surface of the outer shell. The outermost layer canhave a stiffness less than or greater than the stiffness of the outershell. The outermost layer can be configured to resist abrasion, wear,staining, or biological interactions. The outermost layer can have ahardness greater than or equal to about 70 Shore D.

In some embodiments, the appliance further comprises an innermost layercoupled to an inner surface of the inner structure. The innermost layercan have a stiffness less than or greater than the stiffness of theinner structure. The innermost layer can be configured to resistabrasion, wear, staining, or biological interactions. The innermostlayer can have a hardness greater than or equal to about 70 Shore D.

In some embodiments, the inner structure comprises a textured surfaceshaped to channel saliva away from or towards a surface of the at leastone tooth.

In some embodiments, the inner structure is formed by one or more ofmilling, etching, coating, jetting, stereolithography, or printing.Optionally, the inner structure is integrally formed as a single piecewith the outer shell by a direct fabrication technique. Directfabrication techniques can comprise one or more of vatphotopolymerization, material jetting, binder jetting, materialextrusion, powder bed fusion, sheet lamination, or directed energydeposition. The direct fabrication technique can comprise multi-materialdirect fabrication.

In another aspect, a method comprises providing an appliance as in anyof the embodiments herein.

In another aspect, a method for designing an orthodontic appliance forrepositioning a patient's teeth in accordance with a treatment plan isprovided. The method can comprise receiving a 3D representation of ashell comprising a plurality of cavities shaped to receive the patient'steeth, the shell comprising a plurality of shell portions eachpositioned to engage a different subset of the patient's teeth. Themethod can comprise generating a 2D representation corresponding to the3D representation of the shell, the 2D representation representing amaterial sheet to be used to form the shell. The material sheet cancomprise a plurality of sheet portions corresponding to the plurality ofshell portions.

In some embodiments, the 2D representation is generated based on one ormore of cavity geometries for the plurality of cavities, a fabricationmethod to be used to form the shell, a fabrication temperature to beused to form the shell, one or more materials to be used to form theshell, material properties of the one or more materials to be used toform the shell, or a strain rate of the one or more materials to be usedto form the shell. The 2D representation can be generated bytransforming the 3D representation, the transforming comprising one ormore of expanding or flattening the 3D representation. The 2Drepresentation can be generated by simulating a direct or inversedeformation from the 2D representation to the 3D representation

In some embodiments, the method further comprises determining a materialcomposition for each of the plurality of sheet portions. At least someof the plurality of sheet portions can comprise different materialcompositions. The method can further comprise generating instructionsfor fabricating the material sheet comprising the plurality of sheetportions with the determined material compositions, and generatinginstructions for forming the shell from the fabricated material sheet.In some embodiments, the inner shell includes a tooth facing surface andan outer surface of the outer shell is exposed.

In some embodiments, at least some of the plurality of different sheetportions have different geometries. At least some of the plurality ofdifferent sheet portions can have different stiffness. The method canfurther comprise determining a desired stiffness for each of theplurality of sheet portions, and determining the material compositionfor each of the plurality of sheet portions based on the desiredstiffness. The different material compositions can comprise one or moreof: different numbers of material layers, different combinations ofmaterial types, or different thicknesses of a material layer.

In some embodiments, the fabricated material sheet comprises an outerlayer and an inner layer having a stiffness less than a stiffness of theouter layer, and the inner layer is positioned between the outer layerand the patient's teeth when the shell is worn on the patient's teeth.The different material compositions can comprise different thicknessesof the inner layer. The outer layer can be configured to generate atleast one force or torque when the shell is worn on the patient's teethand the inner layer can be configured to distribute the at least oneforce or torque to at least one received tooth.

In some embodiments, fabricating the material sheet comprises providinga layer of a first material, and adding a second material to one or moreportions of the layer. Alternatively or in combination, fabricating thematerial sheet can comprise providing a sheet comprising a layer of afirst material and a layer of a second material, and removing one ormore portions of the layer of the second material. Optionally,fabricating the material sheet comprises coupling a plurality ofoverlapping material layers to form a multilayered material sheet.Fabricating the material sheet can comprise coupling a plurality ofnon-overlapping material sections to form a single-layered materialsheet. Fabricating the material sheet can comprise coupling one or moresupport layers to the single-layered material sheet.

In some embodiments, forming the shell comprises thermoforming thefabricated material sheet over a mold such that the plurality of sheetportions are formed into the plurality of shell portions.

In another aspect, a system for designing an orthodontic appliance forrepositioning a patient's teeth in accordance with a treatment plan isprovided. The system can comprise one or more processors and memory. Thememory can comprise instructions executable by the one or moreprocessors to cause the system to receive a 3D representation of a shellcomprising a plurality of cavities shaped to receive the patient'steeth, the shell comprising a plurality of shell portions eachpositioned to engage a different subset of the patient's teeth. Theinstructions can cause the system to generate a 2D representationcorresponding to the 3D representation of the shell, the 2Drepresentation representing a material sheet to be used to form theshell, and the material sheet comprising a plurality of sheet portionscorresponding to the plurality of shell portions.

In another aspect, a method for designing an orthodontic appliance forrepositioning a patient's teeth is provided. The method can comprisedetermining a movement path to move one or more teeth from an initialarrangement to a target arrangement and determining a force system toproduce movement of the one or more teeth along the movement path. Themethod can comprise determining an appliance geometry for an orthodonticappliance configured to produce the force system. The orthodonticappliance can comprise an outer shell comprising a plurality ofteeth-receiving cavities and an inner structure positioned on an innersurface of the outer shell, the inner structure comprising a stiffnessdifferent than a stiffness of the outer shell such that the innerstructure is configured to exhibit an amount of deformation greater thanan amount of deformation exhibited by the outer shell. The method cancomprise generating instructions for fabricating the orthodonticappliance having the appliance geometry using a direct fabricationtechnique.

In some embodiments, the direct fabrication technique comprises one ormore of vat photopolymerization, material jetting, binder jetting,material extrusion, powder bed fusion, sheet lamination, or directedenergy deposition and may be continuous direct fabrication process,multi-material direct fabrication, or other direct fabrication process.The instructions can be configured to cause a fabrication machine toform the outer shell concurrently with the inner structure.

In some embodiments, the method further comprises determining a materialcomposition for one or more of the outer shell or the inner structure.

In another aspect, an appliance for placing attachments on teeth of apatient is provided. The appliance may include an attachment and asupport. The support may comprise one or more coupling structures tohold the attachment. The appliance may also include one or morealignment structures coupled to the support to receive at least aportion of a tooth and positon the attachment at a predeterminedlocation on the tooth. The one or more coupling structures may beconfigured to release the attachment with removal of the alignmentstructure from the tooth.

In some embodiments, the alignment structure comprises at least aportion of a cavity of an aligner sized and shaped to receive the toothand the support comprises a portion of an aligner extending from theportion of the cavity to a recess. The recess shaped to receive theattachment and comprising one or more coupling structures to hold theattachment, and wherein the at least the portion of the cavity of thealigner and the portion of the aligner extending from the at least theportion of the cavity to the recess have been directly fabricatedtogether. Optionally, the one or more coupling structures comprise oneor more extensions extending between the support and the attachment. Theone or more extensions may absorb infrared light at a rate greater thanthat of the alignment structure.

In some embodiments, the application includes an adhesive on theattachment and may also include a cover on the adhesive. The cover maybe capable of being removed from the adhesive.

In another aspect, a method of fabricating an appliance is provided. Themethod may include directly fabricating an aligner body including asupport formed in a tooth-receiving cavity. The tooth receiving cavitymay be configured to receive a tooth. The method may also includedirectly fabricating one or more coupling structures to the support anddirectly fabricating an attachment to the coupling structure. Thealigner may be configured to align the attachment at a predeterminedlocation on a tooth and the one or more coupling structures may beconfigured to release the attachment with removal of the aligner bodyfrom the tooth.

In some embodiments, the support, the aligner body, and the one or morecoupling structures are directly fabricated together. Optionally, thealignment structure may comprise at least a portion of a cavity of analigner sized and shaped to receive one or more teeth and the supportmay comprise a portion of an aligner including a recess shaped toreceive the attachment. The recess may comprise the one or more couplingstructures to hold the attachment and the aligner body, the one or morecoupling structures, and the recess may be directly fabricated together.

In some embodiments, the one or more coupling structures are configuredto break with removal of the alignment structure from the one or moreteeth. Optionally, the one or more coupling structures may be sized andshaped to hold the attachment. The one or more coupling structures maybe sized and shaped to hold the attachment with a gap extending betweenthe support and the attachment.

In some embodiments, the one or more coupling structures comprise one ormore extensions extending between the support and the attachment. Theone or more coupling structures can include a separator sized and shapedto separate the attachment from the support. The one or more couplingstructures can include a recess formed in the support, the recess sizedand shaped to separate the attachment from the support.

In some embodiments, the method can include forming an adhesivestructure on the attachment. Optionally, the method may include formingan adhesive on the one or more attachments, wherein the adhesive, theone or more coupling structures, the alignment structure, and the one ormore attachment structures are directly fabricated together.

In some embodiments, the method may include forming a cover on theadhesive, the cover capable of removal from the adhesive. The cover, theadhesive, the support, the one or more coupling structures, thealignment structure, and the one or more attachment structures can bedirectly fabricated together. The one or more extensions can be formedwith a material that absorbs infrared light at a rate greater than arate of infrared absorption of the aligner body.

As used herein the term “and/or” is used as a functional word toindicate that two words or expressions are to be taken together orindividually. For example, A and/or B encompasses A alone, B alone, andA and B together.

Turning now to the drawings, in which like numbers designate likeelements in the various figures, FIG. 1A illustrates an exemplary toothrepositioning appliance or aligner 100 that can be worn by a patient inorder to achieve an incremental repositioning of individual teeth 102 inthe jaw. The appliance can include a shell (e.g., a continuous polymericshell or a segmented shell) having teeth-receiving cavities that receiveand resiliently reposition the teeth. In one embodiment, an appliance orportion(s) thereof may be indirectly fabricated using a physical modelof teeth. For example, an appliance (e.g., polymeric appliance) can beformed using a physical model of teeth and a sheet of suitable layers ofpolymeric material. In some embodiments, a physical appliance isdirectly fabricated, e.g., using direct fabrication techniques, from adigital model of an appliance. An appliance can fit over all teethpresent in an upper or lower jaw, or less than all of the teeth. Theappliance can be designed specifically to accommodate the teeth of thepatient (e.g., the topography of the tooth-receiving cavities matchesthe topography of the patient's teeth), and may be fabricated based onpositive or negative models of the patient's teeth generated byimpression, scanning, and the like. Alternatively, the appliance can bea generic appliance configured to receive the teeth, but not necessarilyshaped to match the topography of the patient's teeth. In some cases,only certain teeth received by an appliance will be repositioned by theappliance while other teeth can provide a base or anchor region forholding the appliance in place as it applies force against the tooth orteeth targeted for repositioning. In some cases, many or most, and evenall, of the teeth will be repositioned at some point during treatment.Teeth that are moved can also serve as a base or anchor for holding theappliance as it is worn by the patient. Typically, no wires or othermeans will be provided for holding an appliance in place over the teeth.In some cases, however, it may be desirable or necessary to provideindividual attachments or other anchoring elements 104 on teeth 102 withcorresponding receptacles or apertures 106 in the appliance 100 so thatthe appliance can apply a selected force on the tooth. Exemplaryappliances, including those utilized in the Invisalign® System, aredescribed in numerous patents and patent applications assigned to AlignTechnology, Inc. including, for example, in U.S. Pat. Nos. 6,450,807,and 5,975,893, as well as on the company's website, which is accessibleon the World Wide Web (see, e.g., the url “invisalign.com”). Examples oftooth-mounted attachments suitable for use with orthodontic appliancesare also described in patents and patent applications assigned to AlignTechnology, Inc., including, for example, U.S. Pat. Nos. 6,309,215 and6,830,450.

FIG. 1B illustrates a tooth repositioning system 110 including aplurality of appliances 112, 114, 116. Any of the appliances describedherein can be designed and/or provided as part of a set of a pluralityof appliances used in a tooth repositioning system. Each appliance maybe configured so a tooth-receiving cavity has a geometry correspondingto an intermediate or final tooth arrangement intended for theappliance. The patient's teeth can be progressively repositioned from aninitial tooth arrangement to a target tooth arrangement by placing aseries of incremental position adjustment appliances over the patient'steeth. For example, the tooth repositioning system 110 can include afirst appliance 112 corresponding to an initial tooth arrangement, oneor more intermediate appliances 114 corresponding to one or moreintermediate arrangements, and a final appliance 116 corresponding to atarget arrangement. A target tooth arrangement can be a planned finaltooth arrangement selected for the patient's teeth at the end of allplanned orthodontic treatment. Alternatively, a target arrangement canbe one of many intermediate arrangements for the patient's teeth duringthe course of orthodontic treatment, which may include various differenttreatment scenarios, including, but not limited to, instances wheresurgery is recommended, where interproximal reduction (IPR) isappropriate, where a progress check is scheduled, where anchor placementis best, where palatal expansion is desirable, where restorativedentistry is involved (e.g., inlays, onlays, crowns, bridges, implant,veneers, and the like), etc. As such, it is understood that a targettooth arrangement can be any planned resulting arrangement for thepatient's teeth that follows one or more incremental repositioningstages. Likewise, an initial tooth arrangement can be any initialarrangement for the patient's teeth that is followed by one or moreincremental repositioning stages.

FIG. 2 illustrates a method 200 of orthodontic treatment using aplurality of appliances, in accordance with many embodiments. The method200 can be practiced using any of the appliances or appliance setsdescribed herein. In step 210, a first orthodontic appliance is appliedto a patient's teeth in order to reposition the teeth from a first tootharrangement to a second tooth arrangement. In step 220, a secondorthodontic appliance is applied to the patient's teeth in order toreposition the teeth from the second tooth arrangement to a third tootharrangement. The method 200 can be repeated as necessary using anysuitable number and combination of sequential appliances in order toincrementally reposition the patient's teeth from an initial arrangementto a target arrangement. The appliances can be generated all at the samestage or in sets or batches (e.g., at the beginning of a stage of thetreatment), or one at a time, and the patient can wear each applianceuntil the pressure of each appliance on the teeth can no longer be feltor until the maximum amount of expressed tooth movement for that givenstage has been achieved. A plurality of different appliances (e.g., aset) can be designed and even fabricated prior to the patient wearingany appliance of the plurality. After wearing an appliance for anappropriate period of time, the patient can replace the currentappliance with the next appliance in the series until no more appliancesremain. The appliances are generally not affixed to the teeth and thepatient may place and replace the appliances at any time during theprocedure (e.g., patient-removable appliances). The final appliance orseveral appliances in the series may have a geometry or geometriesselected to overcorrect the tooth arrangement. For instance, one or moreappliances may have a geometry that would (if fully achieved) moveindividual teeth beyond the tooth arrangement that has been selected asthe “final.” Such over-correction may be desirable in order to offsetpotential relapse after the repositioning method has been terminated(e.g., permit movement of individual teeth back toward theirpre-corrected positions). Over-correction may also be beneficial tospeed the rate of correction (e.g., an appliance with a geometry that ispositioned beyond a desired intermediate or final position may shift theindividual teeth toward the position at a greater rate). In such cases,the use of an appliance can be terminated before the teeth reach thepositions defined by the appliance. Furthermore, over-correction may bedeliberately applied in order to compensate for any inaccuracies orlimitations of the appliance.

The ability of an orthodontic appliance to effectively treat a patient'steeth can depend on its properties, such as stiffness, elastic modulus,hardness, thickness, strength, or compressibility. For instance, theseproperties can influence the amount of force and/or torque that can beexerted by the appliance onto the teeth, as well as the extent to whichsuch forces and/or torques can be controlled (e.g., with respect tolocation of application, direction, magnitude, etc.). The optimalproperties for tooth repositioning may vary based on the type of toothto be repositioned (e.g., molar, premolar, canine, incisor), movementtype (e.g., extrusion, intrusion, rotation, torqueing, tipping,translating), targeted movement distance, use of tooth-mountedattachments, or combinations thereof. Different teeth in the patient'sjaw may require different types of appliance properties in order to beeffectively repositioned. In some instances, it can be relativelydifficult to effectively reposition multiple teeth using an orthodonticappliance with uniform and/or homogeneous properties.

Accordingly, various embodiments of the present disclosure provideorthodontic appliances having properties that are heterogeneous and/orvariable across different portions of appliance in order to allow formore effective repositioning of multiple teeth. In such embodiments, oneor more portions of the appliance can have one or more properties thatdiffer from those of one or more other portions, such as with respect toone or more of stiffness, elastic modulus, hardness, thickness,strength, compressibility, and the like. An appliance can include anynumber of portions with different properties, such as two, three, four,five, six, seven, eight, nine, ten, twenty, thirty, forty, fifty, ormore portions with different properties. An appliance portion caninclude any part of an appliance, such as one or more tooth-receivingcavities or portions thereof. The size and location of an applianceportion can be varied as desired. For example, an appliance portion canbe arranged to receive and/or engage a subset of the patient's teeth,such as a single tooth, a plurality of teeth, a portion of a tooth(e.g., a lingual, buccal, or occlusal surface), or combinations thereof.In some embodiments, appliance portions that receive different subsetsof teeth (e.g., anterior teeth, posterior teeth, teeth to berepositioned, teeth to be retained in a current position) have differentproperties. Alternatively or in combination, appliance portions thatengage different surfaces of the teeth (e.g., buccal surfaces, lingualsurfaces, occlusal surfaces) can have different properties. The use oforthodontic appliances with variable localized properties can allow forimproved control over the forces and/or torques to be applied to thepatient's teeth, as described further herein.

In some embodiments, an orthodontic appliance with different localizedproperties is fabricated from a plurality of different materials. Anappliance can be fabricated with one or more of many materials, such asplastics, elastomers, metal, glass, ceramics, reinforced fibers, carbonfiber, composites, reinforced composites, aluminum, biologicalmaterials, or combinations thereof. A material can be incorporated intoan orthodontic appliance in any form, such as a layer, pad, strip, band,wire, mesh, scaffold, or combinations thereof. In some embodiments, anappliance can include at least two, three, four, five, six, seven,eight, nine, or ten different types of materials. Different materialtypes may exhibit different properties (e.g., stiffness, elasticmodulus, etc.). An appliance incorporating multiple materials caninclude different materials at different portions of the appliance so asto provide a desired combination of different localized properties.Exemplary methods for fabricating an appliance with multiple materialsare described further herein.

Optionally, an orthodontic appliance may include only a single materialtype, but can vary the properties of the single material in order toachieve different localized properties. For example, different localizedstiffness can be achieved by varying the thickness and/or the number oflayers of the material at different appliance portions. Alternatively orin combination, the geometry of the material can be selectively alteredat certain locations to modify the corresponding properties of theappliance at that location, e.g., selectively forming cuts or holes toreduce stiffness. These approaches can be used in combination with themulti-material approaches described herein, such that differinglocalized properties can be achieved by varying the material types used,as well as the properties of one or more material types.

In some embodiments, an orthodontic appliance includes at least onerelatively stiff portion and at least one relatively compliant portion.“Stiff” or “relatively stiff” may be used herein to denote an applianceportion having a stiffness greater than a stiffness of another applianceportion, e.g., the rest of the appliance. “Compliant” or “relativelycompliant” may be used herein to denote an appliance portion having astiffness less than a stiffness of another appliance portion, e.g., therest of the appliance. The appliances herein can be fabricated using oneor more types of materials (e.g., synthetic materials such as plastics,ceramics, metals, composites; biological materials such as biologicaltissues, natural materials) with appropriate properties in order toprovide the desired arrangement of stiff and compliant portions. Forinstance, the stiff portion(s) can be fabricated from one or morerelatively stiff materials, and the compliant portion(s) can befabricated from one or more relatively compliant materials. Examples ofstiff materials include but are not limited to plastics, ceramics,metals, composites, or combinations thereof (e.g., a plastic filled withceramic and/or reinforced with metal pieces). Examples of compliantmaterials include but are not limited to elastomers, rubbers, orrubber-like materials.

A stiff portion can have a greater elastic modulus than a compliantportion. In some embodiments, the stiff portion has an elastic modulusof about 1.5 GPa, or within a range from about 0.5 GPa to about 500 GPa.In some embodiments, the compliant portion has an elastic modulus ofabout 2 MPa, or within a range from about 0.2 MPa to about 500 MPa.Optionally, the elastic modulus of a stiff portion can be at least 10times greater than the elastic modulus of a compliant portion. Highmodulus differences between layers can increase the sheer forces at theboundary between layers. In some embodiments, sheer between layers canbe managed by using materials in adjacent layers that differ in elasticmodulus by 10% or less. Alternatively or in combination, a stiff portioncan have a greater thickness than a compliant portion. For example, thestiff portion can have a thickness of about 0.5 mm, or within a rangefrom about 0.2 mm to about 1 mm. The compliant portion can have athickness of about 0.3 mm, or within a range from about 0.05 mm to about0.5 mm. Optionally, the thickness of a stiff portion can be at least 3times greater than the thickness of a compliant portion.

The stiff and compliant portions can perform different functions in theorthodontic appliance. For example, the stiff portion can be used togenerate the forces and/or torques for repositioning the teeth, e.g., bypressing against one or more areas of the teeth. In some embodiments,the appliance is shaped such that the stiff portion is deformed (e.g.,changed in shape) and/or deflected (e.g., changed in position,orientation) when the appliance is worn on the teeth, and the resistanceof the stiff material to the deformation and/or deflection generatesforces and/or torques on the teeth that elicit tooth movements. Thestiff portion can have sufficient stiffness such that different regionscan be deformed and/or deflected with relative independence from eachother (e.g., deformation and/or deflection of one region produces littleor no corresponding deformation and/or deflection in adjacent regions).In some embodiments, the stiff portion is relatively resistant todeformation, such that the stiff portion may be deflected when theappliance is worn on the teeth, but exhibits little or no deformation.Optionally, the stiff portion can be relatively incompressible, suchthat it does not experience significant changes in shape (e.g.,thickness) when the appliance is worn.

The compliant portion can be used to transmit the forces and/or torquesgenerated by the stiff portion to the underlying teeth. For example, thecompliant portion can be positioned between the stiff portion and theteeth (e.g., coupled to an inner surface of the stiff portion facing theteeth) in order to contact the teeth and distribute force and/or torquefrom the stiff portion to the teeth. In some embodiments, the compliantportion is designed to improve the transmission of force and/or torqueto teeth compared to use of the stiff portion alone. For instance, thecompliant portion can improve engagement between the appliance and theteeth, provide a more constant amount of force and/or torque, distributethe force and/or torque over a wider surface area, or combinationsthereof. Optionally, the compliant portion can be relatively deformable(e.g., compressible) so as to exhibit significant changes in shape(e.g., thickness) when the appliance is worn.

The stiff and compliant portions of an orthodontic appliance can bedesigned in a variety of ways. In some embodiments, the stiff portion isan outer appliance shell having a plurality of cavities shaped toreceive teeth, and the compliant portion includes one or more innerstructures coupled to an inner surface of the shell (e.g., an innersurface of one or more tooth-receiving cavities). The compliant innerstructure(s) can be removably coupled or permanently affixed to theouter shell (e.g., via adhesives, fasteners, bonding, etc.). Asdescribed herein, the stiffness of the stiff outer shell can bedifferent from, e.g., greater than, the stiffness of the compliant innerstructure.

The stiff outer shell can be shaped to generate one or more forcesand/or torques in response to the appliance being worn on the patient'steeth. For instance, the outer shell can have an inner surface profile(e.g., an inner surface profile of one or more tooth-receiving cavities)that differs from the surface profile of one or more received teeth(e.g., received within the one or more tooth-receiving cavities. Theinner surface profile of the outer shell can have a different positionand/or orientation than the surface profile of the teeth, for example.Alternatively or in combination, the inner surface profile of the outershell can include structures that do not match the tooth surfaceprofile, such as protrusions extending towards the tooth or recessesextending away from the tooth. The discrepancies between the innersurface profile of the outer shell and the tooth surface profile cancause deflections and/or deformations of the outer shell that generateforces and/or torques that are exerted on the teeth.

The compliant inner structure can be positioned between the outer shelland one or more received teeth in order to distribute the forces and/ortorques generated by the outer shell to the teeth. For example, theinner structure can deform in response to the forces and/or torques,e.g., by exhibiting a change in thickness and/or inner surface profile.Optionally, the inner structure can deform such that the inner surfaceprofile conforms to the surface profile of the tooth, thus increasingthe degree of engagement between the appliance and the tooth surface.This improved engagement can improve force and/or torque transmissionfrom the outer shell to the tooth, e.g., by increasing the tooth surfacearea over which the force and/or torque is applied.

The use of a compliant inner structure to distribute force and/or torquefrom a stiff outer shell can reduce the sensitivity of the orthodonticappliance to variations in manufacturing tolerances. In someembodiments, the geometry of an appliance shell is configured to bedifferent from the geometry of the patient's current tooth arrangement,and the engagement between the shell and the teeth resulting from thisgeometric mismatch, also referred to as “interference,” results inforces and/or torques being exerted on the teeth. The magnitude of theforce and/or torque may correlate with the extent of the interference ofthe shell geometry with the tooth geometry, such that portions of theappliance exhibiting larger amounts of interference apply greateramounts of force and/or torque, while portions exhibiting lessinterference or no interference apply less or no force and/or torque.Accordingly, the appliance geometry can be designed to exhibit certainamounts of interference with the teeth geometry in order to produce thedesired forces and/or torques for repositioning the teeth. Inembodiments where the appliance shell is relatively stiff, deviationsfrom the planned appliance geometry (e.g., due to variations inmanufacturing tolerance) can alter the amount of interference betweenthe stiff shell and the tooth, which in turn can alter the amount offorce and/or torque that is actually applied to the tooth.

The use of a compliant structure with a stiff shell can reduce thesensitivity of the appliance geometry to such variations. In someembodiments, compared to stiffer structures, compliant structures areless susceptible to fluctuations in applied force and/or torque due tomanufacturing tolerances. For example, the amount of force and/or torqueapplied to the tooth by a compliant structure can be less dependent onthe degree of interference between the compliant structure and thetooth, e.g., due to the lower stiffness of the compliant structure. Inorder to produce the same level of force as an entirely stiff appliance,the appliances with compliant structures herein can be designed with anincreased amount of interference with the teeth geometry. Accordingly,orthodontic appliances incorporating compliant structures can producemore consistent and reproducible force and/or torque application onteeth. Additionally, such compliant structures can provide more constantforce application onto the teeth as they move during treatment.

FIGS. 3A and 3B illustrate a portion 300 of an orthodontic applianceincluding a stiff outer shell 302 and a compliant inner structure 304,in accordance with embodiments. FIG. 3A illustrates the applianceportion 300 prior to being placed on the patient's teeth, such that theouter shell 302 and inner structure 304 are both in a free standingunloaded configuration, and the shape profiles of the outer shell 302and inner structure 304 are undistorted. For example, the compliantinner structure 304 (depicted herein as a layer) can have an initialthickness profile 306 and the stiff outer shell 302 can have an initialthickness profile 307. In some embodiments, the undistorted shapeprofile of the outer shell 302 and/or inner structure 304 can correspondto a 3D shape profile of a tooth in an unloaded position and/ororientation prior to being received within the appliance portion 300.

FIG. 3B illustrates the appliance portion 300 after being placed on thepatient's teeth. The portion 300 can engage a tooth 308, such that theinner surface of the inner structure 304 contacts a surface of the tooth308. The inner surface profiles of the inner structure 304 and outershell 302 can differ from the surface profile of the tooth 308, suchthat the appliance portion 300 presses against and applies force to thetooth 308 when the appliance is worn. The stiff outer shell 302 can besufficiently stiff such that it experiences little or no deformationwhen pressed against the tooth 308, e.g., the thickness profile 307 issubstantially unchanged.

In contrast, the compliant inner structure 304 is sufficiently compliantsuch that it is deformed when pressed against the tooth 308. In someembodiments, the compliant inner structure 304 exhibits an amount ofdeformation greater than the amount of deformation exhibited by theouter shell when the appliance is worn on the patient's teeth.Accordingly, when the appliance portion 300 is worn by the patient, theinner structure 304 can assume a loaded configuration different from theunloaded configuration (e.g., with respect to a thickness profile,cross-sectional shape, and/or inner surface profile of the innerstructure 304). For example, the inner structure 304 can be compressedbetween the stiff outer shell 302 and the tooth 308 so as to exhibit analtered (e.g., reduced) thickness profile 310 at the engagement area. Insome embodiments, portions of the inner structure 304 near theengagement region between the inner structure 304 and tooth 308 aresqueezed outward away from the engagement region, such that thethickness profile, inner surface profile, and cross-sectional shape ofthe inner structure 304 is changed relative to the unloadedconfiguration. The distorted shaped profile can correspond to the 3Dshape profile of the tooth 308 when in a received position and/ororientation within the appliance portion 300. The change in thethickness profile of the inner structure 304 can correspond to thedifference between the unloaded position and/or orientation of the tooth308 and the received position and/or orientation of the tooth 308.Optionally, the inner structure 304 can deform so as to conform to thetooth surface profile at the engagement area. The stiffness of the outershell 302 can result in generation of force and/or torque on the tooth308, while the compliance of the inner structure 304 can allow forimproved engagement between the appliance portion 300 and the tooth 308in order to distribute the generated force and/or torque to the tooth308.

The compliant inner structures described herein can be provided invarious forms, such as a layer, pad, strip, band, wire, mesh, scaffold,or combinations thereof. The inner structure can be formed by milling,etching, coating, jetting, printing, bonding, spraying, extrusion,deposition, or combinations thereof, as described further herein. Insome embodiments, the inner structure is a single continuous structure,such as a layer. For example, the inner structure can be a continuouslayer that overlaps the inner surface of the stiff outer shell. Thecompliant inner layer can span some or all of the plurality of cavitiesof the outer shell. In such embodiments, the orthodontic appliance canbe considered a multilayered appliance having a stiff outer layer, and acompliant inner layer.

FIG. 3C illustrates an appliance portion 320, having a compliant toothfacing or inner structure 324 (depicted herein as a layer) and acompliant outer structure 326 while having a stiff middle layer 322,also called a shell. The portion 320 can engage a tooth, such that theinner surface of the inner structure 324 contacts a surface of thetooth. The inner surface profiles of the inner structure 324 and middleshell 322 can differ from the surface profile of the tooth, such thatthe appliance portion 320 presses against and applies force to the toothwhen the appliance is worn. The stiff middle shell 322 can besufficiently stiff such that it experiences little or no deformationwhen pressed against the tooth, e.g., the thickness profile issubstantially unchanged.

In contrast, the compliant inner structure 324, like the inner structure304, is sufficiently compliant such that it is deformed when pressedagainst the tooth. In some embodiments, the compliant inner structure324 exhibits an amount of deformation greater than the amount ofdeformation exhibited by the middle shell 322 when the appliance is wornon the patient's teeth. Accordingly, when the appliance portion 320 isworn by the patient, the inner structure 324 can assume a loadedconfiguration different from the unloaded configuration (e.g., withrespect to a thickness profile, cross-sectional shape, and/or innersurface profile of the inner structure 324). For example, the innerstructure 324 can be compressed between the stiff middle shell 322 andthe tooth so as to exhibit an altered (e.g., reduced) thickness profileat the engagement area. In some embodiments, portions of the innerstructure 324 near the engagement region between the inner structure 324and tooth are squeezed outward away from the engagement region, suchthat the thickness profile, inner surface profile, and cross-sectionalshape of the inner structure 324 is changed relative to the unloadedconfiguration. The distorted shaped profile can correspond to the 3Dshape profile of the tooth when in a received position and/ororientation within the appliance portion 320. The change in thethickness profile of the inner structure 324 can correspond to thedifference between the unloaded position and/or orientation of the toothand the received position and/or orientation of the tooth. Optionally,the inner structure 324 can deform so as to conform to the tooth surfaceprofile at the engagement area. The stiffness of the middle shell 322can result in generation of force and/or torque on the tooth, while thecompliance of the inner structure 324 can allow for improved engagementbetween the appliance portion 320 and the tooth in order to distributethe generated force and/or torque to the tooth and to reduce sensitivityof the force and torque magnitudes due to manufacturing tolerances. Forexample interference between the aligner and the teeth cause the torquesand forces involved in moving the teeth. The elasticity of the alignermaterial and the stiffness of the aligner causes these forces. Smalldifferences in the manufactured shape of an application as compared tothe desired shape of the application can cause deviations from thedesired forces and torques imparted on the teeth. With a stiff aligner,errors in manufacturing magnified as compared to a more compliantaligner. Adding a compliant inner structure can reduce the sensitivityof the force and torque magnitudes due to manufacturing tolerances whilestill maintaining many of the advantages of a stiff aligner, such as theability to impart higher forces and torques on teeth.

The addition of a compliant outer structure 326 may provide a morecomfortable experience for a patient as the compliant outer structure326 may deform upon contact with the gingiva, soft palate, hard palate,cheeks, and other portions of the patient's mouth.

FIG. 4A illustrates a cross-section of an orthodontic appliance 400 witha stiff outer layer 402 and a compliant inner layer 404, in accordancewith embodiments. The outer layer 402 forms a shell with a plurality ofcavities 406 for receiving a patient's teeth, as described herein. Theinner layer 404 is coupled to an inner surface of the outer layer 402,such that the inner layer 404 overlaps some or all of the cavities andis positioned between the outer layer 402 and the received teeth. Insome embodiments, when the appliance 400 is worn on the teeth, thereceived teeth contact the inner layer 404 and do not directly contactthe outer layer 402.

The properties of the inner and outer layers can be varied as desired.In some embodiments, the inner and outer layers have the same thickness,while in other embodiments, the inner and outer layers have differentthicknesses. For instance, the thickness of the outer layer can be about0.5 mm, or within a range from about 0.1 mm to about 2 mm, and thethickness of the inner layer can be about 0.5 mm, or within a range fromabout 0.1 mm to about 2 mm. Optionally, the total thickness of theappliance including both the outer layer and inner layer can be lessthan or equal to about 0.8 mm (e.g., in order to avoid causing open biteif the appliance covers the occlusal areas of tooth crowns). In someembodiments, each layer has a uniform thickness, while in otherembodiments, one or more of the layers can have a non-uniform thickness(e.g., different layer portions have different thicknesses).

In some embodiments, the inner and/or outer layer can include a forcemodifying structure that modulates the localized force and/or torqueapplied to a specified location on the patient's teeth, either directly(e.g., by direct contact with the tooth surface) or indirectly (e.g.,via contact with an attachment mounted on the tooth). A force modifyingstructure can include any structural feature that produces an alterationin a force and/or torque applied to the teeth, such as a thickenedportion, a thinned portion, a protrusion (e.g., ridge, dimple, andindentation), a recess, an aperture, a gap, or combinations thereof. Forexample, a thickened portion or a protrusion that is compressed by thetooth when the appliance is worn can produce a localized increase inforce and/or torque. A thinned portion or a recess can exhibit reducedcontact with the tooth and thus produce a localized decrease in forceand/or torque. The use of force modifying structures as described hereinallow for increased control over force and/or torque application atspecified locations on the teeth.

An appliance can include any number and combination of force modifyingstructures situated on the inner and/or outer layers. In someembodiments, the force modifying structure is located on only the innerlayer or only the outer layer, such that the two layers have differentgeometries. For example, the inner layer can include one or moreportions of increased thickness that are designed to preferentiallyengage the tooth in order to apply force and/or torque. Alternatively orin combination, the inner layer can include one or more portions ofdecreased thickness that reduce localized engagement of the appliancewith the tooth. As another example, the outer layer can be formed withone or more protrusions extending into the tooth receiving cavity inorder to engage and apply force and/or torque to the tooth.Alternatively or in combination, the outer layer can be formed with oneor more recesses or gaps to reduce the amount of force and/or torquethat would be applied. Optionally, the layer that does not include theforce modifying structure can have a uniform thickness.

FIG. 4B illustrates a cross-section of an orthodontic appliance 410having a compliant inner layer 412 with a thickened portion 420, inaccordance with embodiments. The inner layer 412 is coupled to an innersurface of a stiff outer layer 414 so as to define a cavity 416 shapedto receive a tooth 418. The outer layer 414 can have a uniformthickness. The inner layer 412 can include at a force modifyingstructure, such as at least one layer portion 420 with increasedthickness relative to the other portions of the inner layer 412. Thethickened portion 420 can be positioned to engage the received tooth418. Due to the increased thickness of the layer portion 420, when thetooth 418 is received within the cavity 416, the portion 420 may bepressed by the tooth 416 against the stiff outer layer 414. Thisarrangement can result in forces and/or torques being applied to thetooth 418 primarily at the thickened layer portion 420. Multiplethickened portions can be included in the inner layer 412 in order tofacilitate force and/or torque application at multiple differentportions of the tooth 418. Although FIG. 4B illustrates an inner layer412 with a non-uniform thickness and an outer layer with a uniformthickness, one of skill in the art would appreciate that otherembodiments can incorporate an outer layer with a non-uniform thicknessand an inner layer with uniform thickness. In alternative embodiments,both the inner and outer layers can have non-uniform thicknesses.

FIG. 4C illustrates a cross-section of an orthodontic appliance 430including a protrusion 432 formed in the stiff outer layer 434, inaccordance with embodiments. Similar to other embodiments herein, theappliance 430 can include a stiff outer layer 434 coupled to a compliantinner layer 436 so as to define a cavity 438 shaped to receive a tooth440. The outer layer 434 and the inner layer 436 can both have uniformthicknesses. In some embodiments, the stiff outer layer 434 includes aforce modifying structure, such as a protrusion 432 extending inwardsinto the cavity 438 towards the tooth 440. The inner layer 436 canconform to the inner surface profile of the outer layer 434 includingthe protrusion 432. The protrusion 432 can press against the surface ofthe received tooth 440 so as to apply forces and/or torques to thetooth. Optionally, the appliance 430 can include multiple protrusions432 in the outer layer 434 in order to facilitate force and/or torqueapplication at multiple different portions of the tooth 440. AlthoughFIG. 4C illustrates a protrusion 432 in the outer layer 434, one ofskill in the art would appreciate that other embodiments can include aprotrusion in the inner layer, or protrusions in both layers.

In some embodiments, the stiff outer layer and compliant inner layer areremovably coupled to each other, such that the outer and inner layerscan be separated from each other without damaging the appliance. Theremovable coupling can be a snap fit or interference fit, for example.In such embodiments, the inner layer can be considered to be an innershell and the outer layer can be considered to be an outer shell, withthe two shells being separable from each other. To assemble theappliance, the inner shell can be placed on the patient's teeth,followed by placement of the outer shell over the inner shell and ontothe teeth. Alternatively, the inner shell can be inserted into the outershell, and the assembled appliance placed onto the teeth as a singlecomponent. The use of removably coupled inner and outer shells allowsfor a treatment system in which a single inner shell is used withmultiple outer shells, a single outer shell is used with multiple innershells, or combinations thereof. The inner and/or outer shell to be usedcan vary based on the specific treatment stage, such that the patientwears different combinations of shells throughout the course oftreatment.

FIG. 4D illustrates a treatment system 450 including a plurality ofstiff outer shells 452 a-c and a single compliant inner shell 454, inaccordance with embodiments. A single outer shell can be worn over theinner shell 454 in order to form an orthodontic appliance. The stiffouter shells 452 a-c can be shaped to generate tooth repositioningforces and/or torques, while the compliant inner shell 454 can serveprimarily as a liner that engages the teeth to distribute the generatedforce and/or torque to the teeth. In some embodiments, each outer shellcorresponds to a different treatment stage of a treatment plan, suchthat the outer shells 452 a-c are sequentially worn in order toreposition the teeth according to the treatment plan. For instance, thecavity geometries of each outer shell can be shaped according to theparticular tooth arrangement to be achieved with the correspondingtreatment stage. The inner shell 454 can be reusable between treatmentstages, such that the patient can progress to the next stage simply byexchanging the current outer shell for the next one in the sequencewhile maintaining the same inner shell 454. In alternative embodiments,a plurality of compliant inner shells can be used with a single reusablestiff outer shell, with each compliant inner shell corresponding to adifferent treatment stage. One of ordinary skill in the art wouldappreciate that an orthodontic treatment system can include anycombination of reusable outer and inner shells that are combined withnon-reusable inner and outer shells, respectively, to enable a desiredcourse of treatment.

In some embodiments, the stiff outer layer and compliant inner layer arepermanently affixed to each other, such that the layers cannot beseparated without damaging the appliance. The benefits of this approachinclude easier handling and avoiding curling or incorrect positioning ofthe inner layer when worn under the outer layer. An orthodontictreatment plan can involve sequentially applying a plurality ofdifferent multilayered appliances in order to reposition the patient'steeth. Optionally, a treatment plan can include some stages whereappliances with permanently affixed layers are used and some stageswhere appliances with separable shells are used.

Alternatively or in combination with the layer-based approachespresented herein, a compliant inner structure of an orthodonticappliance can include a plurality of discrete structures that arecoupled to certain portions of the outer shell. Examples of suchstructures include but are not limited to pads, plugs, balloons, bands,springs, scaffolds, meshes, or combinations thereof. The appliance caninclude any number of discrete compliant structures positioned at anysuitable location in the shell. The use of one or more discrete innerstructures located at different portions of the appliance enables forcesand/or torques to be controllably applied to selected portions of theteeth. The positioning, geometries (e.g., shape, size), and properties(e.g., stiffness, elastic modulus) of the discrete structure can bevaried as desired in order to achieve a desired force and/or torquedistribution on the teeth.

FIG. 5A illustrates an appliance 500 with a plurality of discrete padstructures 502 coupled to an inner surface of an outer shell 504, inaccordance with embodiments. Similar to other embodiments herein, theouter shell 504 defines a tooth-receiving cavity for a tooth 506. Theplurality of discrete pad structures 502 are positioned between theouter shell 504 and tooth 506 so as to engage the tooth 506. The padstructures 502 may be solid. Alternatively, the pad structures 502 maybe hollow, as discussed further herein. In some embodiments, each padstructure 502 engages a different portion of the tooth 506, such as adifferent tooth surface (e.g., buccal, lingual, or occlusal surface).The discrete pad structures 502 can be configured to transmit forcesand/or torques generated by the outer shell 504 to the differentportions of the tooth 506. In some embodiments, the pad structures 502are formed by printing or spraying onto the inner surface of the outershell 504. Optionally, the pad structures 502 can be formed separatelyfrom and coupled to the outer shell 504, e.g., using adhesives,fasteners, etc. In some embodiments, the pad structures 502 and outershell 504 are formed using direct fabrication, as discussed furtherherein.

FIG. 5B illustrates an appliance 520 with a plurality of discrete plugstructures 522 extending through an outer shell 524, in accordance withembodiments. The appliance 520 is similar to the appliance 500, exceptthat the discrete plug structure 522 each include an outer portion thatextends through the thickness of the outer shell 524. In someembodiments, the discrete plug structures 522 are formed separately fromand coupled to the outer shell 524, e.g., using adhesives, fasteners,etc. Optionally, the discrete plug structures 522 can be coupled to theshell 524 using mechanical retention (e.g., interference fits, snapfits) without adhesives or other attachment elements. The use ofmechanical retention can allow for increased flexibility in the geometryof the discrete plug structures 522. For example, the discrete plugstructures 522 can be hollowed out (e.g., to control stiffness) withoutinterfering with their ability to couple to the outer shell 524. In someembodiments, the plug structures 522 and outer shell 524 are formedusing direct fabrication, as discussed further herein.

FIG. 5C illustrates an appliance 540 with a plurality of discrete hollowor inflatable structures 542, in accordance with embodiments. Theinflatable structure 542 can be a hollow balloon or bladder that can befilled with a fluid, such as a liquid or a gas. The fluid pressure canbe used to control the amount of force and/or torque applied to thereceived tooth 546 by the appliance 540. Optionally, the fluid can bemaintained at a substantially constant pressure so as to allow forsubstantially constant force and/or torque application on the tooth 546.Alternatively, the fluid pressure can be as desired to produce variableforce and/or torque application on the tooth 546.

FIG. 5D illustrates an exemplary load-displacement curve 560 for anappliance, in accordance with embodiments. The load-displacement curve560 exhibits a relatively flattened region 562 in which the force ortorque in the appliance is substantially constant, e.g., does not varysubstantially with increasing displacement. In some embodiments,substantially constant means that the force or torque does not vary bymore than 5%, 10%, 20%, 30%, 40%, or 50% of the maximum value of theforce or torque over the displacement range of interest. The use ofdiscrete compliant inner structures as described herein can allow forapplication of substantially constant forces and/or torques, which canimprove the reliability and consistency of orthodontic treatment withappliances. For example, as described herein with respect to FIG. 5C,one or more structures can be filled with a fluid maintained at asubstantially constant pressure in order to apply substantially constantforce and/or torque to teeth. Alternatively or in combination, adiscrete pad structure can be fabricated in a shape and/or from anappropriate material to produce substantially constant force and/ortorque over a relatively large range of deflections and/or deformationswithout yielding (e.g., polyolefins or shape memory alloys such as NiTor Cu—Al—Ti).

FIG. 5E illustrates an appliance 570 with a plurality of discrete padstructures 572 coupled to an inner surface of an outer shell 574, inaccordance with embodiments. Similar to other embodiments herein, theouter shell 574 defines a tooth-receiving cavity for a tooth 576. Theplurality of discrete pad structures 572 are positioned between theouter shell 574 and tooth 576 so as to engage the tooth 576. The padstructures 572 may be solid. Alternatively, the pad structures 572 maybe hollow, as discussed further herein. In some embodiments, each padstructure 572 engages a different portion of the tooth 576, such as adifferent tooth surface (e.g., buccal, lingual, or occlusal surface).The discrete pad structures 572 can be configured to transmit anddistribute forces and/or torques generated by the outer shell 574 to thedifferent portions of the tooth 576. In some embodiments, the padstructures 572 are distributed about the surface of the outer shell 574such that they distribute the repositioning forces from the outer shell574 onto the tooth 576. In some embodiments, the pad structures 572 areformed by printing or spraying onto the inner surface of the outer shell574. Optionally, the pad structures 572 can be formed separately fromand coupled to the outer shell 574, e.g., using adhesives, fasteners,etc. In some embodiments, the pad structures 572 and outer shell 574 areformed using direct fabrication.

FIG. 5F illustrates an appliance 580 with a compliant layer 582 coupledto an inner surface of an outer shell 574. The compliant layer 582includes a plurality of pad structures 588, in accordance withembodiments. Similar to other embodiments herein, the outer shell 584defines a tooth-receiving cavity for a tooth 586. The plurality of padstructures 588 are positioned on the compliant layer 582 and between theouter shell 584 and tooth 586 so as to engage the tooth 586. Thecompliant layer 582 and pad structures 588 may be solid. In someembodiments, the compliant layer 582 and the pad structures 588 may be asingle, integral structure. In some embodiments, the compliant layer 582and pad structures 588 may be discrete structures. In some embodiments,the pad structures 588 and compliant layer 582 may be hollow. In someembodiments, each pad structure 588 engages a different portion of thetooth 586, such as a different tooth surface (e.g., buccal, lingual, orocclusal surface). The pad structures 588 can be configured to transmitand distribute forces and/or torques generated by the outer shell 584 tothe different portions of the tooth 586. In some embodiments, the padstructures 588 are distributed about the compliant structure 582 suchthat they distribute the repositioning forces from the outer shell 584onto the tooth 586. In some embodiments, the pad structures 588 areformed by printing or spraying onto the inner surface of the outer shell584. Optionally, the pad structures 588 and compliant structure 582 canbe formed separately from and coupled to the outer shell 584, e.g.,using adhesives, fasteners, etc. In some embodiments, the pad structures588, compliant structure 582, and outer shell 584 are formed usingdirect fabrication.

FIG. 5G illustrates an appliance 590 with a plurality of discrete padstructures 592 coupled to an inner surface of an outer shell 594 and aninner surface of an inner shell 591, in accordance with embodiments. Theinner surface of the shell 591 defines a tooth-receiving cavity for atooth 596. The plurality of discrete pad structures 592 are positionedbetween the outer shell 594 and the inner shell 591 and modulate theengagement of the inner shell 591 with the tooth 596. The pad structures592 distribute the repositioning forces of the outer shell 594 onto theinner shell 591 which transmits the forces onto the tooth 596. The padstructures 592 may be solid. Alternatively, the pad structures 592 maybe hollow, as discussed further herein. The discrete pad structures 592can be configured to transmit forces and/or torques generated by theouter shell 574 to the different portions of the inner shell 591 and thetooth 576. In some embodiments, the pad structures 592 are formed byprinting or spraying onto the inner surface of the outer shell 594. Insome embodiments, the pad structures 592 are formed by printing orspraying onto the surface of the inner shell 591. Optionally, the padstructures 592 can be formed separately from and coupled to the outershell 594 or the inner shell 591, e.g., using adhesives, fasteners, etc.In some embodiments, the pad structures 592, inner shell 591, and outershell 594 are formed using direct fabrication.

FIG. 511 illustrates an appliance 550 with a plurality of discrete padstructures 552 coupled to an inner surface of an outer shell 554 whichdefines a tooth-receiving cavity for a tooth 556, similar to theembodiment shown in FIG. 5E. Additional, the appliance 550 includes afilling material 558 between the pad structures 552. This fillingmaterial 558 may be relatively compliant material such that it impartsvery little force or torque on the teeth, for example, it may have anelastic modulus that is ½ or 1/10 of the elastic modulus of the padstructures and/or the outer shell 554. In some embodiments, the fillingmaterial 558 extremely soft, for example, in some embodiments thefilling material 558 may be a viscus fluid, such as a gel, with a thin,stiff outer surface or cover over the filling material on the toothfacing surface. In some embodiments, the filling material may have anelastic modulus of 1/20 or even 1/100 of the elastic modulus of the padstructures.

In some embodiments, the filling material 558 is chosen based on itsoptical properties. For example, the index of refraction of the fillingmaterial 558 may match the index of refraction of the pad structures. Insome embodiments, matching the index of refraction includes matching itsuch that the pad structures 552 are not readily observable on a patientduring normal use. In some embodiments, the index of refraction of thefilling material 558 is within 10% of the index of refraction of the padstructures 552.

Some embodiments of the compliant inner structures described hereindirectly contact the tooth surface in order to transmit forces and/ortorques. In other embodiments, rather than directly contacting the toothsurface, the compliant inner structure engages the tooth indirectly viaone or more attachments mounted to the tooth surface. The geometry andlocation of the inner structure and/or attachment can be designed toproduce a specified force and/or torque when the appliance is worn onthe teeth. The use of attachments can be beneficial for improvingcontrol over the applied force and/or torque, as well as to elicit toothmovements that would otherwise be difficult to produce with an applianceshell only. An appliance can include any number of inner structuresconfigured to engage a corresponding number of attachments mounted onthe patient's teeth.

FIG. 6A illustrates an appliance 600 including an inner structure 602engaging a tooth-mounted attachment 604, in accordance with embodiments.The inner structure 602 can be a compliant discrete pad element coupledto an inner surface of a stiff outer shell 606, as described herein.When the appliance 600 is worn by the patient, the inner structure 602can contact an attachment 604 affixed to a received tooth 608, thustransmitting forces and/or torques produced by the outer shell 606 tothe tooth 608 via the attachment 604. Optionally, the stiff outer shell606 can include a recess 610 shaped to receive and accommodate theattachment 604 when engaged with the inner structure 602. In someembodiments, the attachment 604 is stiffer than the inner structure 602,such that the inner structure 602 is compressed between the outer shell606 and the attachment 604. The inner structure 602 can exhibitspring-like resistance to the compression to exert force onto theattachment 604 that is transmitted to the underlying tooth 608. Thisapproach can provide tooth repositioning forces with greaterreproducibility.

Various embodiments herein provide a compliant inner structure that iscoupled to the stiff outer shell, and not to a tooth or an attachment.Alternatively, the inner structure can be coupled to a tooth surface oran attachment affixed to a tooth surface, and not to the outer shell. Insome embodiments, an inner structure mounted on a tooth can beconsidered to be a compliant attachment. The geometry and location ofthe compliant attachment can be designed to engage the stiff outer shellin order to transmit forces and/or torques generated by the stiff outershell to the underlying tooth.

FIG. 6B illustrates an appliance 620 including a compliant tooth-mountedattachment 622, in accordance with embodiments. The compliant attachment622 is mounted on a surface of a tooth 624 received within a cavitydefined by a stiff outer shell 626 of the appliance 620. The stiff outershell 626 can include a recess 628 accommodating the compliantattachment 622. When the appliance 620 is worn over the patient's teeth,the stiff outer shell 626 can engage the attachment 622, and theattachment 622 can distribute the forces and/or torques produced by thestiff outer shell 626 to the underlying tooth 624. The use of acompliant attachment 622 can provide improved control over the amount offorce and/or torque exerted on the tooth 624 compared to stiffattachments.

In some embodiments, a compliant inner structure can be provided with aprotective layer to reduce wear. The protective layer can be formed as amaterial layer or as a coating deposited on the compliant innerstructure. The protective layer can have a greater stiffness and/orhardness than the inner structure in order to protect the innerstructure against abrasion. In some embodiments, the protective layer isformed on one or more exposed surfaces of the compliant inner structure,such as an exposed surface that is arranged to engage a relatively stiffand/or hard object. For instance, for a compliant inner structurecoupled to an inner surface of a stiff outer shell, the protective layercan be formed on a surface of the inner structure that engages areceived tooth or attachment. As another example, for a compliant innerstructure coupled to a tooth or tooth-mounted attachment, the protectivelayer can be formed on a surface of the inner structure that engages astiff outer shell. This approach may be particularly beneficial forcompliant structures that are mounted on a tooth surface (e.g.,compliant attachment) or attachment surface, since such structures aremore likely to be subjected to abrasive forces associated with jawmovements such as chewing.

In some embodiments, a stain resistant protective layer may be formed ona surface of the aligner. The stain resistant protective layer may be animpermeable or semi-permeable layer that resists staining from fluids,such as coffee and soda, food, and other things.

In some embodiments, a biological compatible layer is provided on anexternal portion of the aligner. For example, some patients may have asensitivity, such as an allergy, to certain materials, such as, forexample, latex. To reduce the likelihood of an allergic reaction in apatient, an aligner may be formed with biological compatible layer thatprovides a barrier between a potentially harmful material, such as anallergen, and the patient's tissue.

Some compliant and stiff structures may be susceptible to wear anddamage caused by fluids in the mouth. For example, saliva may weaken analigner structure, increasing the rate at which it wears and reducingits stiffness. Therefore, in some embodiments, a saliva resistant layermay be formed on one or more surfaces of an aligner structure to resistwear caused by saliva. In some embodiments, the aligner may include ahydrophobic or hydrophilic layer or coating.

In some embodiments, multiple protective layers may be used. Forexample, a stain resistant protective layer may be formed over a wearresistant protective layer.

FIG. 6C illustrates a compliant attachment-mounted structure 640 with aprotective layer 642, in accordance with embodiments. In the depictedembodiment, the compliant structure 640 is a pad structure coupled to asurface of an attachment 644 mounted on a tooth 646. The attachment 644can be relatively stiff and/or hard compared to the compliant structure640. The compliant structure 640 can be positioned so as to engage astiff outer shell (not shown) that receives the tooth 646 and attachment644. The protective layer 642 can be formed on a surface of thecompliant structure 640 that would contact the stiff outer shell, thusprotecting the compliant structure 640 from wear due to abrasion by thestiff outer shell.

An orthodontic appliance incorporating a compliant inner structurecoupled to a stiff outer shell can allow for relatively independentapplication of forces and/or torques on different teeth. In someembodiments, this can be achieved by increasing the stiffness of theouter shell so as to reduce the extent to which deformation and/ordeflection of one shell portion causes deformation and/or deflection ofother shell portions. In such embodiments, the outer shell may besignificantly stiffer than shells used in other types of orthodonticappliances. For example, an appliance configured for independent forceand/or torque application can include an outer shell with an elasticmodulus of about 2.5 GPa, or within a range from about 1 GPa to about 25GPa. In some embodiments, increased stiffness can be achieved byincreasing the thickness of the outer shell. A plurality of compliantinner structures can be coupled to the stiff outer shell so as totransmit forces and/or torques to individual teeth or subsets of teeth,in accordance with the methods provided herein. Such appliances canallow force and/or torque application to be customized on a per-toothbasis and improve predictability of effects on neighboring teeth.

FIGS. 7A, 7B, and 7C schematically illustrate independent forceapplication on teeth, in accordance with embodiments. FIG. 7Aillustrates an appliance 700 in which the outer shell includes a stifflingual portion 702. In alternative embodiments, the appliance 700 caninclude a stiff buccal portion rather than a stiff lingual portion. Aplurality of compliant inner structures (depicted schematically assprings 704) are coupled to an inner surface of the lingual portion 702,with each inner structure positioned to engage a single tooth 706. Thelingual portion 702 can be sufficiently stiff such that forces and/ortorques can be independently applied to each tooth 706 via therespective inner structure. FIG. 7B illustrates an appliance 720 similarto the appliance 700, except that the outer shell includes a stiffbuccal portion 722 in addition to a stiff lingual portion 724. Compliantinner structures (depicted schematically as springs 726) can be coupledto the buccal portion 722 and/or the lingual portion 724 in order toengage individual teeth 728 and transmit forces and/or torques. FIG. 7Cillustrates an appliance 740 similar to the application 700, except thatthe outer shell is a stiff buccal portion 742, rather than a stifflingual portion. Compliant inner structures (depicted schematically assprings 744) are coupled to an inner surface of the buccal portion 742,with each inner structure positioned to engage a single tooth 746. Thebuccal portion 742 can be sufficiently stiff that forces and/or torquescan be independently applied to each tooth 746 via the respectivestructure.

In alternative embodiments, an orthodontic appliance configured forindependent force and/or torque application can include a plurality ofdiscrete stiff shell segments each receiving a subset of teeth, ratherthan the continuous stiff shell portions depicted in FIGS. 7A, 7B, and7C. The shell segments can be coupled to each other via flexures orother connecting elements that permit relative movement of the segments.The use of discrete shell segments can further insulate subsets of teethfrom being affected by forces and/or torques applied to other subsets.

In some embodiments, the surface properties of the compliant innerstructure can be modulated to further improve contact between theappliance and received teeth. In some embodiments, the inner structureis formed from a tacky or high friction material to aid in creatingtangential forces and/or torques on the tooth surface. Alternatively orin combination, the inner structure can have a textured surface shapedto control movement of saliva relative to the tooth surface, e.g., bychanneling it away from or towards the tooth surface. For instance,channeling saliva away from the area of engagement can allow for higherfriction contact between the appliance and tooth surface. Surfacetextures for removing saliva can include pointed structures, voids orother sponge-like structures, flexible channels that deform to pushsaliva out, or combinations thereof. In other embodiments, channelingsaliva towards the engagement area can increase surface tension betweenthe appliance and the teeth, which can improve force and/or torquedelivery to the teeth. Surface textures for channeling saliva towardsthe engagement area can include channels shaped to draw in and retainsaliva by capillary action. Optionally, alterations in surfaceproperties can be achieved by applying a coating with the desiredproperties to the inner structure, rather than varying the properties ofthe inner structure itself.

The orthodontic appliances provided herein can include other componentsin addition to a stiff outer shell and compliant inner structure. Insome embodiments, an appliance can further include one or moreadditional layers coupled to the outer surface of the outer shell, andthese layers can perform various different functions. For example, theappliance can include an outermost layer coupled to the outer surface ofthe outer shell. The outermost layer can be less stiff than the outershell in order to provide cushioning for teeth of the opposing jaw,improve patient comfort, and/or aid in settling the appliance on theteeth. Alternatively or in combination, the outermost layer can have agreater stiffness and/or hardness than the outer shell, e.g., in orderto protect the appliance, against abrasion, wear, staining, biologicalinteractions (e.g., reduce plaque or biological growth), and the like.For example, the outermost layer can have a hardness greater than orequal to about 70 Shore D or about 90 Shore D. In some embodiments, theproperties of the outermost layer are selected to improve the aestheticsof the appliance. Appliances with localized variations in geometry(e.g., non-uniform thicknesses, protrusion, recesses, etc.) may have aless aesthetic appearance due to non-uniform optical properties, such asreflectivity. Accordingly, the outermost layer can be designed toprovide a relatively smooth outer surface in order to improve theexternal appearance of the appliance. The outermost layer can be thinnerthan the outer shell and/or inner structure in order to reduce thecontributions of the outermost layer to the overall properties of theappliance.

Similarly, in some embodiments, an appliance can further include one ormore additional layers coupled to the inner surface of the outer shelland/or inner structure, and these layers can perform various differentfunctions. For example, the appliance can include an innermost layercoupled to an inner surface of the inner structure, and the innermostlayer can be stiffer and/or harder than the inner structure, e.g., toprotect the inner structure from abrasion, wear, staining, biologicalinteractions, and the like. The innermost layer can have a hardnessgreater than or equal to about 70 Shore D or about 90 Shore D, forinstance. Alternatively, the innermost layer can be less stiff than theinner structure in order to provide cushioning for teeth of the opposingjaw, improve comfort, etc. The innermost layer can be thinner than theouter shell and/or inner structure in order to reduce the contributionsof the innermost layer to the overall properties of the appliance.

The present disclosure provides various methods for fabricating theorthodontic appliances with different localized properties describedherein. As discussed herein, such appliances can be produced by usingmultiple materials (e.g., a relatively stiff material and a relativelycompliant material), with the different portions having differentmaterial compositions and/or geometries. In some embodiments, theappliances herein (or portions thereof) can be produced using indirectfabrication techniques, such as by thermoforming over a positive ornegative mold. Indirect fabrication of an orthodontic appliance caninvolve producing a positive or negative mold of the patient's dentitionin a target arrangement (e.g., by additive manufacturing, milling, etc.)and thermoforming one or more sheets of material over the mold in orderto generate an appliance shell. In some embodiments, an appliance isfabricated by producing a material sheet with different portions havingdifferent localized properties, then forming (e.g., thermoforming) thematerial sheet over a mold (e.g., a positive mold of a tootharrangement) to produce a shell. Optionally, additional materialaddition and/or removal steps can occur after the shell has been formedin order to generate the final appliance.

In order to ensure that forces and/or torques are accurately generatedand applied to the appropriate teeth, it is important that the differentappliance portions are correctly positioned relative to the underlyingteeth. The positioning of the appliance portions in the final appliancecan depend on how the different portions are positioned on the materialsheet used to form the appliance. Accordingly, it can be beneficial todetermine spatial correspondences between locations on the materialsheet, portions of the appliance, and portions of the patient's teeth inorder to ensure accurate appliance fabrication.

FIG. 8A illustrates spatial correspondences between a patient's teeth800, an orthodontic appliance 802, and a material sheet 804, inaccordance with embodiments. As described herein, the appliance 802 caninclude a shell with a plurality of teeth-receiving cavities each shapedto receive a respective tooth of the patient's jaw. The appliance 802can be formed from a material sheet 804, e.g., by thermoforming over amold. Accordingly, each tooth can be spatially mapped to a correspondingshell portion of the appliance 802, and each shell portion can bespatially mapped to a corresponding sheet portion of the material sheet804. For example, in the depicted embodiment, tooth 806 is receivedwithin a shell portion 808, which is formed from sheet portion 810. Thespatial mappings can then be used as a basis for fabricating thematerial sheet 804.

FIG. 8B illustrates a material sheet 820 for forming an appliance, inaccordance with embodiments. The material sheet 820 can include aplurality of different sheet portions 822, each corresponding to arespective shell portion of an appliance to be formed from the sheet820. Different sheet portions 822 of the material sheet 820 can havedifferent properties (e.g., thickness, stiffness, elastic modulus,etc.), as indicated by the different shading in FIG. 8B, such that theformed appliance has shell portions with different properties. Forexample, different sheet portions can have different materialcompositions, such that the material type(s) used to form each sheetportion can vary. Alternatively or in combination, different sheetportions 822 can utilize the same material(s) but can vary the geometry(e.g., thickness) of the material(s) so as to achieve differentproperties. In some embodiments, a sheet portion 822 may be mapped toone or more teeth, for example, sheet portion 822 a is elongated and ismapped to two teeth and sheet portion 822 b is elongated and is mappedto three teeth.

In some embodiments, the different properties are uniform across a sheetportion 822. In some embodiments, the different properties may bevariable within a sheet portion 822 or across the material sheet 820.For example, FIG. 8C and FIG. 8D show examples of variable propertiesacross the sheet 820 and the individual sheet portions 822. FIG. 8Cshows a cross section though the sheet 820 and sheet portions 822 d and822 c. The sheet portion 822 d shows an example of a sheet portionhaving a step change at its edges and a variable convex shape across theportion 822 d, from one side to the other. The sheet portion 822 c showsan example of a sheet portion having a concave shape, wherein thethickness varies from one side to the other, but without a step changeat its edges. The thickness profile and cross-sectional shape of thesheet portions 822 and the material sheet 820 may vary according to thedesired properties of the resulting appliance.

FIG. 8D shows another cross section through the sheet 820 and four sheetportions 822 a, 822 d, 822 e, 822 f of FIG. 8B. Sheet portion 822 a isan example of a sheet portion 822 with a step change at its edges, butwith a continuous thickness, while sheet portion 822 d is an example ofa sheet portion with a step change at its edges, but a variablethickness along its length, having a first thickness at one edge and asecond thickness at its other edge. Sheet portion 822 e is an example ofa constant thickness sheet portion, while sheet portion 822 f is anexample of a concave, variable thickness sheet portion with continuousthickness change at its edges.

FIG. 9 illustrates a method 900 for designing and fabricating anorthodontic appliance, in accordance with embodiments. In someembodiments, the method 900 is a computer-based method, such that someor all of the steps of the method 900 are performed by one or moreprocessors of a computing device or system.

In step 910, a 3D representation of a shell is received. The 3Drepresentation can be a 3D digital model, for example. The shell caninclude a plurality of cavities shaped to receive the patient's teeth asdescribed herein. In some embodiments, the shell includes a plurality ofshell portions each positioned to receive and engage a different subsetof the patient's teeth (e.g., a single tooth, multiple teeth, a portionof a tooth). The 3D representation can depict the 3D geometry of anappliance shell for a treatment stage of an orthodontic treatment plan.The 3D geometry can be generated based on a digital representation ofthe patient's teeth in a desired tooth arrangement, as described herein.

In step 920, a 2D representation of a material sheet to be used to formthe shell is generated. The 2D representation can correspond to the 3Drepresentation of the shell, such that the 3D representation is used asa basis for generating the 2D representation. In some embodiments, the3D representation is transformed, e.g., by “flattening” or “expanding,”in order to produce the 2D representation. The transformation procedurecan be based on the expected behavior of the material sheet during theforming process. For example, the transformation method can account forfactors such as the geometries of the teeth-receiving cavities, thefabrication method to be used to form the shell, the fabricationtemperature to be used, the material(s) to be used, material propertiesof the material(s) to be used (e.g., strain rate), or combinationsthereof. Alternatively or in combination, step 920 can involvedetermining correspondences between individual points on the 2Drepresentation of the material sheet to points on the 3D representationof the shell by simulating or emulating the direct or inversedeformation from the 2D sheet geometry to the 3D shell geometry.

The material sheet can include a plurality of sheet portions eachcorresponding to a respective shell portion, and the 2D representationcan include information indicating these spatial correspondences. Thespatial correspondences can be determined, for example, by trackingvarious points on the 3D representation during the transformationprocedure to determine their final locations in the 2D representation.Thus, each sheet portion in the 2D representation can be mapped to acorresponding shell portion in the 3D representation. The 2Drepresentation of the sheet can then be updated, processed, and/ormodified at selected locations to selectively and locally modify theproperties of the 3D shell to be formed, as discussed further herein.

In step 930, a material composition is determined for the materialsheet. The material sheet can be formed from a plurality of overlappingmaterial layers, a plurality of non-overlapping material sections, orcombinations thereof, as described further herein. In some embodiments,a material composition is determined for each of the plurality of sheetportions, with at least some of the sheet portions having differentmaterial compositions (e.g., different number of material layers,different combinations of material types, different thicknesses of amaterial layer, etc.). For instance, some sheet portions can befabricated using a compliant material coupled to a stiff material, whileother portions can be fabricated using a stiff material only, such thatthe resultant appliance is a stiff outer shell with coupled compliantinner structures at certain locations. Optionally, at least some of thesheet portions can have different geometries (e.g., shapes, thicknesses,etc.).

As described herein, different shell portions of an appliance can bedesigned to have different properties in order to apply forces and/ortorques to specific subsets of teeth. In order to achieve this, thesheet portions corresponding to the shell portions can be fabricatedwith different properties. The material composition for each sheetportion can be determined based on the desired properties for thatparticular portion. For example, a desired stiffness can be determinedfor each sheet portion, and the material composition of each sheetportion can be determined based on the desired stiffness.

In step 940, instructions are generated for fabricating the materialsheet. The instructions can be transmitted to a fabrication system, suchas a 3D printer or computer numerical control (CNC) milling machine. Theinstructions can cause the fabrication system to fabricate the materialsheet having the sheet portions with the material compositionsdetermined in step 930. The fabrication procedure can involve additivemanufacturing processes, subtractive manufacturing processes, orcombinations thereof. For example, the material sheet can be fabricatedby milling, etching, coating, jetting, printing, bonding, spraying,extrusion, deposition, or combinations thereof. In some embodiments, thematerial sheet is fabricated using direct fabrication techniques, asdiscussed further herein.

In step 950, instructions are generated for forming the shell from thefabricated material sheet. The instructions can be transmitted to aforming system, such as a thermoforming system. In such embodiments, theshell can be formed by thermoforming the fabricated material sheet overa mold, such that the plurality of sheet portions of the material sheetare formed into the plurality of shell portions of the shell. In someembodiments, the step 950 involves accurately aligning the fabricatedmaterial sheet to the mold in order to ensure that the shell is formedwith the desired material compositions at the intended locations.

The method 900 can be used to produce any embodiment of the appliancesdescribed herein, such as an appliance having a stiff outer shell and acompliant inner structure. For example, the method 900 can be used tofabricate a material sheet having a stiff outer layer and a compliantinner layer. The material sheet can have sheet portions with differentmaterial compositions, such as different thicknesses of the compliantinner layer. The material sheet can be formed into a shell, such thatthe compliant inner layer is positioned between the stiff outer layerand the patient's teeth when the shell is worn by the patient. The stiffouter layer can be configured to generate a force and/or torque when theshell is worn, and the compliant inner layer can be configured todistribute the force and/or torque to one or more teeth received withinthe shell.

Although the above steps show method 900 of designing and fabricating inaccordance with embodiments, a person of ordinary skill in the art willrecognize many variations based on the teaching described herein. Someof the steps may comprise sub-steps. Some of the steps may be optional,such as one or more of steps 930, 940, or 950. The order of the stepsmay be varied as desired. For instance, in alternative embodiments, step950 could be performed after step 920 and before step 930.

FIG. 10A illustrates an additive manufacturing process 1000 forfabricating an appliance, in accordance with embodiments. The process1000 can be used in combination with any of the appliance fabricationmethods described herein (e.g., the method 900). In step 1010, amaterial sheet including a layer of a first material is provided. Thefirst material can be a relatively stiff material, for instance. In step1020, a second, different material is added to one or more portions ofthe first layer. The second material can be a relatively compliantmaterial, for instance. The second material can be applied, for example,by selective coating, jetting, printing, stereolithography techniques,bonding, extruding, or combinations thereof in order to produce adesired shape profile (e.g., a single continuous layer, a plurality ofdiscrete structures, variable thicknesses, etc.). Optionally, the step1020 can be repeated as desired to add any number of materials to thesheet. Alternatively, rather than using different materials, the process1000 can involve joining multiple layers of the same material. Thenumber and/or thickness of the material layers can be varied in order toproduce the desired properties. In some embodiments, the steps 1010 and1020 are performed using one or more of the direct fabricationtechniques described herein. In step 1030, the material sheet is formedinto a shell shaped to be worn over the teeth. For example, a sheetformed from a stiff first material and compliant second material can bemolded such that first material forms an outer shell and the secondmaterial is located in the interior of the shell.

FIG. 10B illustrates a subtractive manufacturing process 1050 forfabricating an appliance, in accordance with embodiments. The process1050 can be used in combination with any of the appliance fabricationmethods described herein (e.g., the method 900). In step 1060, amaterial sheet is provided including a first layer of a first materialand a second layer of a second material. The first material can be arelatively stiff material and the second material can be a relativelycompliant material for instance. In step 1070, one or more portions ofthe second layer are removed. The second layer portions can be removed,for example, by milling, chemical etching, laser etching, orcombinations thereof in order to produce a desired shape profile (e.g.,a single continuous layer, a plurality of discrete structures, variablethicknesses, etc.). Optionally, the step 1070 can also involve removingone or more portions of the first layer. In step 1080, the materialsheet is formed into a shell shaped to be worn over the teeth. Forexample, the first layer can form an appliance shell and the secondlayer can be located in the interior of the shell.

FIGS. 11A and 11B illustrate fabrication of a material sheet from aplurality of overlapping material layers 1100 a-d, in accordance withembodiments. A plurality of overlapping material layers 1100 a-d can beprovided, as depicted in FIG. 11A (illustrating a cross-sectional view).Some or all of the material layers 1100 a-d can be made from differentmaterial types and/or have different properties, as indicated by thedifferent shading in the depicted embodiment. Alternatively, some or allof the material layers 1100 a-d can be made from the same material typeand/or have the same properties. In some embodiments, the coverage areaof some or all of the layers differ from each other. For example, in thedepicted embodiment, layer 1100 a spans the entire material sheet, whilelayers 1100 b-d only partially span the material sheet. Layers withpartial coverage can be fabricated in a variety of ways, e.g., byselective removal of one or more layer portions from a larger layer,fabricating the layer to include only the desired portions, etc.

The material layers 1100 a-d can be coupled together to form amultilayered material sheet 1102, as shown in FIG. 11B. The differentlayers 1100 a-d can be sequentially coupled to each other, or can all becoupled together simultaneously. In some embodiments, the material sheet1102 is formed using the direct fabrication techniques described herein.The fabricated material sheet 1102 can include multiple layers ofdifferent materials, with different material compositions at differentlocations according to the coverage of each individual material layer.Different portions of the material sheet 1102 can have differentthicknesses, based on the number and/or the thicknesses of the layersused to form each portion. In some embodiments, a material sheet mayhave two, three, four, or more layers of similar or different materials.

FIGS. 12A through 12C illustrate fabrication of a material sheet from aplurality of non-overlapping material sections 1200 a-c, in accordancewith embodiments. A plurality of non-overlapping material sections 1200a-c can be provided, as depicted in FIG. 12A (illustrating across-sectional view). Some or all of the material sections 1200 a-c canbe made from different material types and/or have different properties,as indicated by the different shading in the depicted embodiment. Insome embodiments, the coverage area of some or all of the sectionsdiffer from each other. For example, in the depicted embodiment, each ofthe sections 1200 a-c spans a different portion of the material sheet.

The material sections 1200 a-c can be coupled together to form asingle-layered material sheet 1202, as shown in FIG. 12B. The differentsections 1200 a-c can be sequentially coupled to each other, can all becoupled together simultaneously. In alternative embodiments, thematerial sheet 1202 can be fabricated without first providing discretematerial sections 1200 a-c, e.g., by using a printing process orselective coating to apply different materials at different locations.In some embodiments, the material sheet 1202 is formed using thedirection fabrication techniques described herein. The fabricatedmaterial sheet 1202 can include different material compositions atdifferent sheet portions, according to the location of each materialsection.

Optionally, one or more support layers 1204 can be coupled to thesingle-layered material sheet 1202, resulting in a multi-layeredmaterial sheet 1206. The support layer 1204 can be used to reinforce thesingle-layered material sheet 1202, particularly at or near the areaswhere the different material sections 1200 a-c are joined together. Insome embodiments, a single support layer 1204 is used. Alternatively,multiple support layers can be used, e.g., coupled to the upper andlower surfaces of the single-layered material sheet 1202 so as toenclose the sheet 1202. The support layer can be relatively thincompared to the single-layered material sheet 1202 so as to providelittle or no effect on the stiffness of the final sheet 1206. Thisapproach can be used to provide a stronger sheet and reduce thelikelihood of breakage or separation between the different materialsections 1200 a-c.

The various embodiments of the orthodontic appliances presented hereincan be fabricated in a wide variety of ways. In some embodiments, theorthodontic appliances herein (or portions thereof) are produced usingdirect fabrication, such as additive manufacturing techniques (alsoreferred to herein as “3D printing”) or subtractive manufacturingtechniques (e.g., milling). In some embodiments, direct fabricationinvolves forming an object (e.g., an orthodontic appliance or a portionthereof) without using a physical template (e.g., mold, mask etc.) todefine the object geometry. Additive manufacturing techniques can becategorized as follows: (1) vat photopolymerization (e.g.,stereolithography), in which an object is constructed layer by layerfrom a vat of liquid photopolymer resin; (2) material jetting, in whichmaterial is jetted onto a build platform using either a continuous ordrop on demand (DOD) approach; (3) binder jetting, in which alternatinglayers of a build material (e.g., a powder-based material) and a bindingmaterial (e.g., a liquid binder) are deposited by a print head; (4)fused deposition modeling (FDM), in which material is drawn though anozzle, heated, and deposited layer by layer; (5) powder bed fusion,including but not limited to direct metal laser sintering (DMLS),electron beam melting (EBM), selective heat sintering (SHS), selectivelaser melting (SLM), and selective laser sintering (SLS); (6) sheetlamination, including but not limited to laminated object manufacturing(LOM) and ultrasonic additive manufacturing (UAM); and (7) directedenergy deposition, including but not limited to laser engineering netshaping, directed light fabrication, direct metal deposition, and 3Dlaser cladding. For example, stereolithography can be used to directlyfabricate one or more of the appliances herein. In some embodiments,stereolithography involves selective polymerization of a photosensitiveresin (e.g., photopolymer) according to a desired cross-sectional shapeusing light (e.g., ultraviolet light). The object geometry can be builtup in a layer-by-layer fashion by sequentially polymerizing a pluralityof object cross-sections. As another example, the appliances herein canbe directly fabricated using selective laser sintering. In someembodiments, selective laser sintering involves using a laser beam toselectively melt and fuse a layer of powdered material according to adesired cross-sectional shape in order to build up the object geometry.As yet another example, the appliances herein can be directly fabricatedby fused deposition modeling. In some embodiments, fused depositionmodeling involves melting and selectively depositing a thin filament ofthermoplastic polymer in a layer-by-layer manner in order to form anobject. In yet another example, material jetting can be used to directlyfabricate the appliances herein. In some embodiments, material jettinginvolves jetting or extruding one or more materials onto a build surfacein order to form successive layers of the object geometry.

In some embodiments, the direct fabrication methods provided hereinbuild up the object geometry in a layer-by-layer fashion, withsuccessive layers being formed in discrete build steps. Alternatively orin combination, direct fabrication methods that allow for continuousbuild-up of an object geometry can be used, referred to herein as“continuous direct fabrication.” Various types of continuous directfabrication methods can be used. As an example, in some embodiments, theappliances herein are fabricated using “continuous liquid interphaseprinting,” in which an object is continuously built up from a reservoirof photopolymerizable resin by forming a gradient of partially curedresin between the building surface of the object and apolymerization-inhibited “dead zone.” In some embodiments, asemi-permeable membrane is used to control transport of aphotopolymerization inhibitor (e.g., oxygen) into the dead zone in orderto form the polymerization gradient. Continuous liquid interphaseprinting can achieve fabrication speeds about 25 times to about 100times faster than other direct fabrication methods, and speeds about1000 times faster can be achieved with the incorporation of coolingsystems. Continuous liquid interphase printing is described in U.S.Patent Publication Nos. 2015/0097315, 2015/0097316, and 2015/0102532,the disclosures of each of which are incorporated herein by reference intheir entirety.

As another example, a continuous direct fabrication method can achievecontinuous build-up of an object geometry by continuous movement of thebuild platform (e.g., along the vertical or Z-direction) during theirradiation phase, such that the hardening depth of the irradiatedphotopolymer is controlled by the movement speed. Accordingly,continuous polymerization of material on the build surface can beachieved. Such methods are described in U.S. Pat. No. 7,892,474, thedisclosure of which is incorporated herein by reference in its entirety.

In another example, a continuous direct fabrication method can involveextruding a composite material composed of a curable liquid materialsurrounding a solid strand. The composite material can be extruded alonga continuous three-dimensional path in order to form the object. Suchmethods are described in U.S. Patent Publication No. 2014/0061974, thedisclosure of which is incorporated herein by reference in its entirety.

In yet another example, a continuous direct fabrication method utilizesa “heliolithography” approach in which the liquid photopolymer is curedwith focused radiation while the build platform is continuously rotatedand raised. Accordingly, the object geometry can be continuously builtup along a spiral build path. Such methods are described in U.S. PatentPublication No. 2014/0265034, the disclosure of which is incorporatedherein by reference in its entirety.

In some embodiments, the orthodontic appliances herein are formed usingboth direct fabrication and indirect fabrication techniques. Forinstance, a direct fabrication technique (e.g., vat photopolymerization,material jetting, binder jetting, material extrusion, powder bed fusion,sheet lamination, or directed energy deposition) can be used to form afirst portion of the appliance, and an indirect fabrication technique(e.g., thermoforming) can be used to form a second portion of theappliance. In some embodiments, a direct fabrication technique is usedto produce a material sheet with variable material properties and/orcompositions as described herein, and an indirect fabrication techniqueis used to form the material sheet into the appliance.

The direct fabrication approaches provided herein are compatible with awide variety of materials, including but not limited to one or more ofthe following: a polyester, a co-polyester, a polycarbonate, athermoplastic polyurethane, a polypropylene, a polyethylene, apolypropylene and polyethylene copolymer, an acrylic, a cyclic blockcopolymer, a polyetheretherketone, a polyamide, a polyethyleneterephthalate, a polybutylene terephthalate, a polyetherimide, apolyethersulfone, a polytrimethylene terephthalate, a styrenic blockcopolymer (SBC), a silicone rubber, an elastomeric alloy, athermoplastic elastomer (TPE), a thermoplastic vulcanizate (TPV)elastomer, a polyurethane elastomer, a block copolymer elastomer, apolyolefin blend elastomer, a thermoplastic co-polyester elastomer, athermoplastic polyamide elastomer, or combinations thereof. Thematerials used for direct fabrication can be provided in an uncured form(e.g., as a liquid, resin, powder, etc.) and can be cured (e.g., byphotopolymerization, light curing, gas curing, laser curing,crosslinking, etc.) in order to form an orthodontic appliance or aportion thereof. The properties of the material before curing may differfrom the properties of the material after curing. Once cured, thematerials herein can exhibit sufficient strength, stiffness, durability,biocompatibility, etc. for use in an orthodontic appliance. Thepost-curing properties of the materials used can be selected accordingto the desired properties for the corresponding portions of theappliance.

In some embodiments, relatively rigid portions of the orthodonticappliance can be formed via direct fabrication using one or more of thefollowing materials: a polyester, a co-polyester, a polycarbonate, athermoplastic polyurethane, a polypropylene, a polyethylene, apolypropylene and polyethylene copolymer, an acrylic, a cyclic blockcopolymer, a polyetheretherketone, a polyamide, a polyethyleneterephthalate, a polybutylene terephthalate, a polyetherimide, apolyethersulfone, and/or a polytrimethylene terephthalate.

In some embodiments, relatively elastic portions of the orthodonticappliance can be formed via direct fabrication using one or more of thefollowing materials: a styrenic block copolymer (SBC), a siliconerubber, an elastomeric alloy, a thermoplastic elastomer (TPE), athermoplastic vulcanizate (TPV) elastomer, a polyurethane elastomer, ablock copolymer elastomer, a polyolefin blend elastomer, a thermoplasticco-polyester elastomer, and/or a thermoplastic polyamide elastomer.

Optionally, the direct fabrication methods described herein allow forfabrication of an appliance including multiple materials, referred toherein as “multi-material direct fabrication.” In some embodiments, amulti-material direct fabrication method involves concurrently formingan object from multiple materials in a single manufacturing step. Forinstance, a multi-tip extrusion apparatus can be used to selectivelydispense multiple types of materials (e.g., resins, liquids, solids, orcombinations thereof) from distinct material supply sources in order tofabricate an object from a plurality of different materials. Suchmethods are described in U.S. Pat. No. 6,749,414, the disclosure ofwhich is incorporated herein by reference in its entirety. Alternativelyor in combination, a multi-material direct fabrication method caninvolve forming an object from multiple materials in a plurality ofsequential manufacturing steps. For instance, a first portion of theobject can be formed from a first material in accordance with any of thedirect fabrication methods herein, then a second portion of the objectcan be formed from a second material in accordance with methods herein,and so on, until the entirety of the object has been formed. Therelative arrangement of the first and second portions can be varied asdesired, e.g., the first portion can be partially or wholly encapsulatedby the second portion of the object.

Direct fabrication can provide various advantages compared to othermanufacturing approaches. For instance, in contrast to indirectfabrication, direct fabrication permits production of an orthodonticappliance without utilizing any molds or templates for shaping theappliance, thus reducing the number of manufacturing steps involved andimproving the resolution and accuracy of the final appliance geometry.Additionally, direct fabrication permits precise control over thethree-dimensional geometry of the appliance, such as the appliancethickness. Complex structures and/or auxiliary components can be formedintegrally as a single piece with the appliance shell in a singlemanufacturing step, rather than being added to the shell in a separatemanufacturing step. In some embodiments, direct fabrication is used toproduce appliance geometries that would be difficult to create usingalternative manufacturing techniques, such as appliances with very smallor fine features, complex geometric shapes, undercuts, interproximalstructures, shells with variable thicknesses, and/or internal structures(e.g., for improving strength with reduced weight and material usage).For example, in some embodiments, the direct fabrication approachesherein permit fabrication of an orthodontic appliance with feature sizesof less than or equal to about 5 μm, or within a range from about 5 μmto about 50 μm, or within a range from about 20 μm to about 50 μm.

Direct fabrication can provide improved control over the geometry andmaterial properties of the appliance in three dimensions. In someembodiments, the direct fabrication techniques described herein can beused to produce appliances with substantially isotropic materialproperties, e.g., substantially the same or similar strengths along alldirections. In some embodiments, the direct fabrication techniquesdescribed herein can be used to produce appliances with anisotropicmaterial properties. For example, the layers of material that form anappliance may include layers of material having differentdirectionality. For example, a first layer may include a polymermaterial having polymer chains arranged in substantially a firstdirection while a second layer may include a polymer material havingpolymer chains arranged in substantially a second direction, the firstdirection being different than the second direction. In someembodiments, the direct fabrication approaches herein permit productionof an orthodontic appliance with a strength that varies by no more thanabout 25%, about 20%, about 15%, about 10%, about 5%, about 1%, or about0.5% along all directions. Alternatively, direct fabrication can be usedto fabricate appliances with anisotropic and/or heterogeneous materialproperties, such as appliances with both stiff portions (e.g., a stiffouter shell) and compliant portions (e.g., a compliant inner structure),as discussed herein. For instance, the appliances with structurespresented herein such as multiple layers (see, e.g., FIGS. 4A through4C), a plurality of discrete pad structures (see, e.g., FIG. 5A, aplurality of discrete plug structures (see, e.g., FIG. 5B), a pluralityof discrete inflatable structures (see, e.g., FIG. 5C),attachment-engaging structures (see, e.g., FIG. 6A), tooth-mountedattachments (see, e.g., FIG. 6B), attachment-mounted structures (see,e.g., FIG. 6C), and/or attachment templates (see, e.g., FIGS. 17A and17B) can be easily produced using direct fabrication techniques.

In some embodiments, the appliances of the present disclosure areproduced through the use of multi-material direct fabrication to depositdifferent types of materials at locations where different properties aredesired. For instance, a relatively stiff or rigid material can bedeposited at locations where increased stiffness is desired (e.g., astiff outer shell), and a relatively compliant or elastic material canbe deposited at locations where increased compliance is desired (e.g., acompliant inner structure). The production of an appliance from multiplematerials can be performed concurrently in a single manufacturing step,or in a plurality of sequential steps, as discussed above and herein. Insome embodiments, the compliant inner structure is formed concurrentlyand integrally with the stiff outer shell, rather than being coupled tothe shell in a separate step after the shell has already been produced.

Alternatively or in combination, the appliances herein are producedthrough the use of direct fabrication techniques that vary the geometryof the appliance at locations where different properties are desired.For example, a direct fabrication process can selectively vary thethickness of the formed material in order to control the resultantstiffness of the appliance, e.g., such that stiffer portions of theappliance have an increased thickness compared to more compliantportions of the appliance. As another example, stiffness-modulatingstructures such as apertures, slits, perforations, etchings, and thelike can be selectively formed at certain locations in the appliance inorder to reduce the local stiffness at those locations. Directfabrication permits formation of such structures integrally andconcurrently with formation of the appliance, such that separate cuttingor etching steps are not needed. In yet another example, directfabrication process parameters such as curing parameters (e.g., curingtime, energy, power, spacing, depth) can be selectively varied in orderto influence the stiffness and/or other properties of the material. Inmany embodiments, control over the curing parameters is used to controlthe degree of crosslinking of the formed material, which in turncontributes to the local stiffness (e.g., increased crosslinkingproduces increased stiffness, reduced crosslinking produces reducedstiffness).

Additionally, the direct fabrication approaches herein can be used toproduce orthodontic appliances at a faster speed compared to othermanufacturing techniques. In some embodiments, the direct fabricationapproaches herein allow for production of an orthodontic appliance in atime interval less than or equal to about 1 hour, about 30 minutes,about 25 minutes, about 20 minutes, about 15 minutes, about 10 minutes,about 5 minutes, about 4 minutes, about 3 minutes, about 2 minutes,about 1 minutes, or about 30 seconds. Such manufacturing speeds allowfor rapid “chair-side” production of customized appliances, e.g., duringa routine appointment or checkup.

In some embodiments, the direct fabrication methods described hereinimplement process controls for various machine parameters of a directfabrication system or device in order to ensure that the resultantappliances are fabricated with a high degree of precision. Suchprecision can be beneficial for ensuring accurate delivery of a desiredforce system to the teeth in order to effectively elicit toothmovements. Process controls can be implemented to account for processvariability arising from multiple sources, such as the materialproperties, machine parameters, environmental variables, and/orpost-processing parameters.

Material properties may vary depending on the properties of rawmaterials, purity of raw materials, and/or process variables duringmixing of the raw materials. In many embodiments, resins or othermaterials for direct fabrication should be manufactured with tightprocess control to ensure little variability in photo-characteristics,material properties (e.g., viscosity, surface tension), physicalproperties (e.g., modulus, strength, elongation) and/or thermalproperties (e.g., glass transition temperature, heat deflectiontemperature). Process control for a material manufacturing process canbe achieved with screening of raw materials for physical propertiesand/or control of temperature, humidity, and/or other process parametersduring the mixing process. By implementing process controls for thematerial manufacturing procedure, reduced variability of processparameters and more uniform material properties for each batch ofmaterial can be achieved. Residual variability in material propertiescan be compensated with process control on the machine, as discussedfurther herein.

Machine parameters can include curing parameters. For digital lightprocessing (DLP)-based curing systems, curing parameters can includepower, curing time, and/or grayscale of the full image. For laser-basedcuring systems, curing parameters can include power, speed, beam size,beam shape and/or power distribution of the beam. For printing systems,curing parameters can include material drop size, viscosity, and/orcuring power. These machine parameters can be monitored and adjusted ona regular basis (e.g., some parameters at every 1-x layers and someparameters after each build) as part of the process control on thefabrication machine. Process control can be achieved by including asensor on the machine that measures power and other beam parametersevery layer or every few seconds and automatically adjusts them with afeedback loop. For DLP machines, gray scale can be measured andcalibrated before, during, and/or at the end of each build, and/or atpredetermined time intervals (e.g., every n^(th) build, once per hour,once per day, once per week, etc.), depending on the stability of thesystem. In addition, material properties and/or photo-characteristicscan be provided to the fabrication machine, and a machine processcontrol module can use these parameters to adjust machine parameters(e.g., power, time, gray scale, etc.) to compensate for variability inmaterial properties. By implementing process controls for thefabrication machine, reduced variability in appliance accuracy andresidual stress can be achieved.

In many embodiments, environmental variables (e.g., temperature,humidity, Sunlight or exposure to other energy/curing source) aremaintained in a tight range to reduce variable in appliance thicknessand/or other properties. Optionally, machine parameters can be adjustedto compensate for environmental variables.

In many embodiments, post-processing of appliances includes cleaning,post-curing, and/or support removal processes. Relevant post-processingparameters can include purity of cleaning agent, cleaning pressureand/or temperature, cleaning time, post-curing energy and/or time,and/or consistency of support removal process. These parameters can bemeasured and adjusted as part of a process control scheme. In addition,appliance physical properties can be varied by modifying thepost-processing parameters. Adjusting post-processing machine parameterscan provide another way to compensate for variability in materialproperties and/or machine properties.

The configuration of the orthodontic appliances herein can be determinedaccording to a treatment plan for a patient, e.g., a treatment planinvolving successive administration of a plurality of appliances forincrementally repositioning teeth. Computer-based treatment planningand/or appliance manufacturing methods can be used in order tofacilitate the design and fabrication of appliances. For instance, oneor more of the appliance components described herein can be digitallydesigned and fabricated with the aid of computer-controlledmanufacturing devices (e.g., computer numerical control (CNC) milling,computer-controlled additive manufacturing such as direct jetting,etc.). The computer-based methods presented herein can improve theaccuracy, flexibility, and convenience of appliance fabrication.

FIG. 15 illustrates a method 1500 for designing an orthodontic applianceto be produced by direct fabrication, in accordance with embodiments.The method 1500 can be applied to any embodiment of the orthodonticappliances described herein. Some or all of the steps of the method 1500can be performed by any suitable data processing system or device, e.g.,one or more processors configured with suitable instructions.

In step 1510, a movement path to move one or more teeth from an initialarrangement to a target arrangement is determined. The initialarrangement can be determined from a mold or a scan of the patient'steeth or mouth tissue, e.g., using wax bites, direct contact scanning,x-ray imaging, tomographic imaging, sonographic imaging, and othertechniques for obtaining information about the position and structure ofthe teeth, jaws, gums and other orthodontically relevant tissue. Fromthe obtained data, a digital data set can be derived that represents theinitial (e.g., pretreatment) arrangement of the patient's teeth andother tissues. Optionally, the initial digital data set is processed tosegment the tissue constituents from each other. For example, datastructures that digitally represent individual tooth crowns can beproduced. Advantageously, digital models of entire teeth can beproduced, including measured or extrapolated hidden surfaces and rootstructures, as well as surrounding bone and soft tissue.

The target arrangement of the teeth (e.g., a desired and intended endresult of orthodontic treatment) can be received from a clinician in theform of a prescription, can be calculated from basic orthodonticprinciples, and/or can be extrapolated computationally from a clinicalprescription. With a specification of the desired final positions of theteeth and a digital representation of the teeth themselves, the finalposition and surface geometry of each tooth can be specified to form acomplete model of the tooth arrangement at the desired end of treatment.

Having both an initial position and a target position for each tooth, amovement path can be defined for the motion of each tooth. In someembodiments, the movement paths are configured to move the teeth in thequickest fashion with the least amount of round-tripping to bring theteeth from their initial positions to their desired target positions.The tooth paths can optionally be segmented, and the segments can becalculated so that each tooth's motion within a segment stays withinthreshold limits of linear and rotational translation. In this way, theend points of each path segment can constitute a clinically viablerepositioning, and the aggregate of segment end points can constitute aclinically viable sequence of tooth positions, so that moving from onepoint to the next in the sequence does not result in a collision ofteeth.

In step 1520, a force system to produce movement of the one or moreteeth along the movement path is determined. A force system can includeone or more forces and/or one or more torques. Different force systemscan result in different types of tooth movement, such as tipping,translation, rotation, extrusion, intrusion, root movement, etc.Biomechanical principles, modeling techniques, forcecalculation/measurement techniques, and the like, including knowledgeand approaches commonly used in orthodontia, may be used to determinethe appropriate force system to be applied to the tooth to accomplishthe tooth movement. In determining the force system to be applied,sources may be considered including literature, force systems determinedby experimentation or virtual modeling, computer-based modeling,clinical experience, minimization of unwanted forces, etc.

In step 1530, an appliance geometry for an orthodontic applianceconfigured to produce the force system is determined. The appliance caninclude a stiff outer shell and a compliant inner structure, asdiscussed herein. The step 1530 can involve determining the shape andarrangement of the outer shell and inner structure that would producethe forces and/or torques to be applied to the teeth, in accordance withthe various embodiments presented herein. For instance, compliant innerstructures such as discrete pads or plugs can be positioned toselectively engage the teeth at locations where the forces and/ortorques are to be exerted. Determination of the appliance geometry caninvolve determining geometries for one or more force modifyingstructures formed in the inner structure and/or outer shell in order toapply forces and/or torques at specified contact points on teeth.Optionally, the step 1530 further involves determining a materialcomposition for the outer shell and/or inner structure in order to applythe desired force system with reduced sensitivity to manufacturingvariations, as discussed herein. In some embodiments, the materialcomposition is selected based on the desired properties (e.g.,stiffness) for the shell and/or inner structure.

Determination of the appliance geometry, material composition, and/orproperties can be performed using a treatment or force applicationsimulation environment. A simulation environment can include, e.g.,computer modeling systems, biomechanical systems or apparatus, and thelike. Optionally, digital models of the appliance and/or teeth can beproduced, such as finite element models. The finite element models canbe created using computer program application software available from avariety of vendors. For creating solid geometry models, computer aidedengineering (CAE) or computer aided design (CAD) programs can be used,such as the AutoCAD® software products available from Autodesk, Inc., ofSan Rafael, Calif. For creating finite element models and analyzingthem, program products from a number of vendors can be used, includingfinite element analysis packages from ANSYS, Inc., of Canonsburg, Pa.,and SIMULIA(Abaqus) software products from Dassault Systèmes of Waltham,Mass.

Optionally, one or more appliance geometries can be selected for testingor force modeling. As noted above, a desired tooth movement, as well asa force system required or desired for eliciting the desired toothmovement, can be identified. Using the simulation environment, acandidate appliance geometry can be analyzed or modeled fordetermination of an actual force system resulting from use of thecandidate appliance. One or more modifications can optionally be made toa candidate appliance, and force modeling can be further analyzed asdescribed, e.g., in order to iteratively determine an appliance designthat produces the desired force system.

In step 1540, instructions for fabrication of the orthodontic appliancehaving the appliance geometry are generated. The instructions can beconfigured to control a fabrication system or device in order to producethe orthodontic appliance with the specified appliance geometry. In someembodiments, the instructions are configured for manufacturing theorthodontic appliance using direct fabrication (e.g., stereolithography,selective laser sintering, fused deposition modeling, direct jetting,continuous direct fabrication, multi-material direct fabrication, etc.),in accordance with the various methods presented herein. In alternativeembodiments, the instructions can be configured for indirect fabricationof the appliance, e.g., by thermoforming.

Although the above steps show a method 1500 of designing an orthodonticappliance in accordance with some embodiments, a person of ordinaryskill in the art will recognize some variations based on the teachingdescribed herein. Some of the steps may comprise sub-steps. Some of thesteps may be repeated as often as desired. One or more steps of themethod 1500 may be performed with any suitable fabrication system ordevice, such as the embodiments described herein. Some of the steps maybe optional, and the order of the steps can be varied as desired.

FIG. 13 illustrates a method 1300 for digitally planning an orthodontictreatment and/or design or fabrication of an appliance, in accordancewith many embodiments. The method 1300 can be applied to any of thetreatment procedures described herein and can be performed by anysuitable data processing system. Any embodiment of the appliancesdescribed herein can be designed or fabricated using the method 1300.

In step 1310, a digital representation of a patient's teeth is received.The digital representation can include surface topography data for thepatient's intraoral cavity (including teeth, gingival tissues, etc.).The surface topography data can be generated by directly scanning theintraoral cavity, a physical model (positive or negative) of theintraoral cavity, or an impression of the intraoral cavity, using asuitable scanning device (e.g., a handheld scanner, desktop scanner,etc.).

In step 1320, one or more treatment stages are generated based on thedigital representation of the teeth. The treatment stages can beincremental repositioning stages of an orthodontic treatment proceduredesigned to move one or more of the patient's teeth from an initialtooth arrangement to a target arrangement. For example, the treatmentstages can be generated by determining the initial tooth arrangementindicated by the digital representation, determining a target tootharrangement, and determining movement paths of one or more teeth in theinitial arrangement necessary to achieve the target tooth arrangement.The movement path can be optimized based on minimizing the totaldistance moved, preventing collisions between teeth, avoiding toothmovements that are more difficult to achieve, or any other suitablecriteria.

In step 1330, at least one orthodontic appliance is fabricated based onthe generated treatment stages. For example, a set of appliances can befabricated to be sequentially worn by the patient to incrementallyreposition the teeth from the initial arrangement to the targetarrangement. Some of the appliances can be shaped to accommodate a tootharrangement specified by one of the treatment stages. Alternatively orin combination, some of the appliances can be shaped to accommodate atooth arrangement that is different from the target arrangement for thecorresponding treatment stage. For example, as previously describedherein, an appliance may have a geometry corresponding to anovercorrected tooth arrangement. Such an appliance may be used to ensurethat a suitable amount of force is expressed on the teeth as theyapproach or attain their desired target positions for the treatmentstage. As another example, an appliance can be designed in order toapply a specified force system on the teeth and may not have a geometrycorresponding to any current or planned arrangement of the patient'steeth.

In some instances, staging of various arrangements or treatment stagesmay not be necessary for design and/or fabrication of an appliance. Asillustrated by the dashed line in FIG. 13, design and/or fabrication ofan orthodontic appliance, and perhaps a particular orthodontictreatment, may include use of a representation of the patient's teeth(e.g., receive a digital representation of the patient's teeth 1310),followed by design and/or fabrication of an orthodontic appliance basedon a representation of the patient's teeth in the arrangementrepresented by the received representation.

FIG. 14 is a simplified block diagram of a data processing system 1400that may be used in executing methods and processes described herein.The data processing system 1400 typically includes at least oneprocessor 1402 that communicates with one or more peripheral devices viabus subsystem 1404. These peripheral devices typically include a storagesubsystem 1406 (memory subsystem 1408 and file storage subsystem 1414),a set of user interface input and output devices 1418, and an interfaceto outside networks 1416. This interface is shown schematically as“Network Interface” block 1416, and is coupled to correspondinginterface devices in other data processing systems via communicationnetwork interface 1424. Data processing system 1400 can include, forexample, one or more computers, such as a personal computer,workstation, mainframe, laptop, and the like.

The user interface input devices 1418 are not limited to any particulardevice, and can typically include, for example, a keyboard, pointingdevice, mouse, scanner, interactive displays, touchpad, joysticks, etc.Similarly, various user interface output devices can be employed in asystem of the invention, and can include, for example, one or more of aprinter, display (e.g., visual, non-visual) system/subsystem,controller, projection device, audio output, and the like.

Storage subsystem 1406 maintains the basic required programming,including computer readable media having instructions (e.g., operatinginstructions, etc.), and data constructs. The program modules discussedherein are typically stored in storage subsystem 1406. Storage subsystem1406 typically includes memory subsystem 1408 and file storage subsystem1414. Memory subsystem 1408 typically includes a number of memories(e.g., RAM 1410, ROM 1412, etc.) including computer readable memory forstorage of fixed instructions, instructions and data during programexecution, basic input/output system, etc. File storage subsystem 1414provides persistent (non-volatile) storage for program and data files,and can include one or more removable or fixed drives or media, harddisk, floppy disk, CD-ROM, DVD, optical drives, and the like. One ormore of the storage systems, drives, etc may be located at a remotelocation, such coupled via a server on a network or via theinternet/World Wide Web. In this context, the term “bus subsystem” isused generically so as to include any mechanism for letting the variouscomponents and subsystems communicate with each other as intended andcan include a variety of suitable components/systems that would be knownor recognized as suitable for use therein. It will be recognized thatvarious components of the system can be, but need not necessarily be atthe same physical location, but could be connected via variouslocal-area or wide-area network media, transmission systems, etc.

Scanner 1420 includes any means for obtaining a digital representation(e.g., images, surface topography data, etc.) of a patient's teeth(e.g., by scanning physical models of the teeth such as casts 1421, byscanning impressions taken of the teeth, or by directly scanning theintraoral cavity), which can be obtained either from the patient or fromtreating professional, such as an orthodontist, and includes means ofproviding the digital representation to data processing system 1400 forfurther processing. Scanner 1420 may be located at a location remotewith respect to other components of the system and can communicate imagedata and/or information to data processing system 1400, for example, viaa network interface 1424. Fabrication system 1422 fabricates appliances1423 based on a treatment plan, including data set information receivedfrom data processing system 1400. Fabrication machine 1422 can, forexample, be located at a remote location and receive data setinformation from data processing system 1400 via network interface 1424.

FIG. 16 illustrates a method 1600 for designing an orthodontic applianceto be produced by direct fabrication, in accordance with embodiments.The method 1600 can be applied to any embodiment of the orthodonticappliances described herein. Some or all of the steps of the method 1600can be performed by any suitable data processing system or device, e.g.,one or more processors configured with suitable instructions.

In step 1610, a movement path to move one or more teeth from an initialarrangement to a target arrangement is determined. The initialarrangement can be determined from a mold or a scan of the patient'steeth or mouth tissue, e.g., using wax bites, direct contact scanning,x-ray imaging, tomographic imaging, sonographic imaging, and othertechniques for obtaining information about the position and structure ofthe teeth, jaws, gums and other orthodontically relevant tissue. Fromthe obtained data, a digital data set can be derived that represents theinitial (e.g., pretreatment) arrangement of the patient's teeth andother tissues. Optionally, the initial digital data set is processed tosegment the tissue constituents from each other. For example, datastructures that digitally represent individual tooth crowns can beproduced. Advantageously, digital models of entire teeth can beproduced, including measured or extrapolated hidden surfaces and rootstructures, as well as surrounding bone and soft tissue.

The target arrangement of the teeth (e.g., a desired and intended endresult of orthodontic treatment) can be received from a clinician in theform of a prescription, can be calculated from basic orthodonticprinciples, and/or can be extrapolated computationally from a clinicalprescription. With a specification of the desired final positions of theteeth and a digital representation of the teeth themselves, the finalposition and surface geometry of each tooth can be specified to form acomplete model of the tooth arrangement at the desired end of treatment.

Having both an initial position and a target position for each tooth, amovement path can be defined for the motion of each tooth. In someembodiments, the movement paths are configured to move the teeth in thequickest fashion with the least amount of round-tripping to bring theteeth from their initial positions to their desired target positions.The tooth paths can optionally be segmented, and the segments can becalculated so that each tooth's motion within a segment stays withinthreshold limits of linear and rotational translation. In this way, theend points of each path segment can constitute a clinically viablerepositioning, and the aggregate of segment end points can constitute aclinically viable sequence of tooth positions, so that moving from onepoint to the next in the sequence does not result in a collision ofteeth.

In step 1620, a force system to produce movement of the one or moreteeth along the movement path is determined. A force system can includeone or more forces and/or one or more torques. Different force systemscan result in different types of tooth movement, such as tipping,translation, rotation, extrusion, intrusion, root movement, etc.Biomechanical principles, modeling techniques, forcecalculation/measurement techniques, and the like, including knowledgeand approaches commonly used in orthodontia, may be used to determinethe appropriate force system to be applied to the tooth to accomplishthe tooth movement. In determining the force system to be applied,sources may be considered including literature, force systems determinedby experimentation or virtual modeling, computer-based modeling,clinical experience, minimization of unwanted forces, etc.

In step 1630, an attachment template design for an orthodontic applianceconfigured to produce the force system is determined. Determination ofthe attachment template design, appliance geometry, materialcomposition, and/or properties can be performed using a treatment orforce application simulation environment. A simulation environment caninclude, e.g., computer modeling systems, biomechanical systems orapparatus, and the like. Optionally, digital models of the applianceand/or teeth can be produced, such as finite element models. The finiteelement models can be created using computer program applicationsoftware available from a variety of vendors. For creating solidgeometry models, computer aided engineering (CAE) or computer aideddesign (CAD) programs can be used, such as the AutoCAD® softwareproducts available from Autodesk, Inc., of San Rafael, Calif. Forcreating finite element models and analyzing them, program products froma number of vendors can be used, including finite element analysispackages from ANSYS, Inc., of Canonsburg, Pa., and SIMULIA(Abaqus)software products from Dassault Systèmes of Waltham, Mass.

Optionally, one or more attachment template designs can be selected fortesting or force modeling. As noted above, a desired tooth movement, aswell as a force system required or desired for eliciting the desiredtooth movement, can be identified. Using the simulation environment, acandidate attachment template design can be analyzed or modeled fordetermination of an actual force system resulting from use of thecandidate appliance. One or more modifications can optionally be made toa candidate appliance, and force modeling can be further analyzed asdescribed, e.g., in order to iteratively determine an appliance designthat produces the desired force system.

In step 1640, instructions for fabrication of the orthodontic applianceincorporating the attachment template design are generated. Theinstructions can be configured to control a fabrication system or devicein order to produce the orthodontic appliance with the specifiedattachment template design. In some embodiments, the instructions areconfigured for manufacturing the orthodontic appliance using directfabrication (e.g., vat photopolymerization, material jetting, binderjetting, material extrusion, powder bed fusion, sheet lamination, ordirected energy deposition, etc.), in accordance with the variousmethods presented herein. In alternative embodiments, the instructionscan be configured for indirect fabrication of the appliance, e.g., bythermoforming.

Although the above steps show a method 1600 of designing an orthodonticappliance in accordance with some embodiments, a person of ordinaryskill in the art will recognize some variations based on the teachingdescribed herein. Some of the steps may comprise sub-steps. Some of thesteps may be repeated as often as desired. One or more steps of themethod 1600 may be performed with any suitable fabrication system ordevice, such as the embodiments described herein. Some of the steps maybe optional, and the order of the steps can be varied as desired.

FIG. 17A illustrates a directly fabricated attachment template 1700comprising an attachment, an alignment structure, and a support to holdthe attachment. The template 1700 may comprise an aligner 1701. Thealigner 1701 comprises a support 1703 to hold the attachment withsufficient force to support the attachment. The aligner 1701 isconfigured to receive a tooth and thereby align an attachment on thetooth. The attachment 1702 is designed to attach on a patient's toothand have surfaces shaped to allow the application of tooth-moving forceswhen contacting a surface of an orthodontic appliance. The attachment1702 is held with a support 1703. The support 1703 may define areceptacle with a shape corresponding to the attachment. The support1703 is configured to hold the attachment so that the attachmentcontacts a tooth when the attachment template is worn by a patient. Theattachment is connected to the aligner 1701 by a coupling structure1704, which is configured to hold the attachment 1702 within the support1703 until the attachment is affixed to the patient's tooth. After theattachment 1702 has been bonded to the patient's tooth, the couplingstructure may be broken, as described in further detail below.Alternatively, the attachment can be weakly connected to the aligner,for example with structures such as perforations to facilitate removalof the attachment from the appliance.

In order to adhere to a patient's tooth, the attachment may comprise anadhesive layer 1705 directly deposited on its surface. In someembodiments, the attachment template may not include an adhesive layer1705. In some embodiments, the surface of the patient's tooth may beprepared before the attachment is attached to the tooth, for example,the surface of the tooth may be acid etched. The adhesive layer 1705 maybe directly fabricated along with the remainder of the attachmenttemplate. Useful choices of material from which to fabricate theadhesive layer 1705 may include one or more materials as describedherein. For example, the adhesive may be an ultraviolet (UV) curingadhesive or pressure sensitive adhesive. In some embodiments, theadhesive is omitted.

After contacting the adhesive layer to a tooth, it may be induced toform a bond between the tooth and the attachment 1702, using a methodappropriate to the material chosen, which may for example include suchsteps as photopolymerization, the application of pressure, theapplication of heat, or the chemical reaction of the adhesive materialwith an activator. When dealing with adhesive materials for whichphotopolymerization is to be used, it may be desirable to fabricate thealigner 1701, attachment 1702, and/or other portions of the attachmenttemplate 1700 from transparent materials, permitting applied light tomore efficiently set the adhesive. Alternatively or additionally, insome cases the adhesive layer 1705 may be applied independently, forexample as a separate step of manufacture, or by a dental practitioner.

In some cases, the attachment template may further comprise a cover 1706over the adhesive layer 1705, to protect the adhesive layer 1705 and theattachment 1702. In some instances, the cover 1706 may seal the adhesivelayer and attachment 1702 within the support 1703 prior to attachment toa patient's tooth. During the attachment procedure, the cover may beremoved, for example by pulling on a handle-like portion 1707, to revealthe attachment and adhesive, which may then be contacted to a patient'stooth by placing the attachment template over the patient's tooth.

Each of the aligner 1701, attachment 1702, support 1703, couplingstructure 1704, adhesive 1705, cover 1706, and handle 1707 may bedirectly fabricated as part of a single process as described herein. Thematerials for each of these components can be chosen independently.Typically, the attachment 1702 will comprise a rigid material; thealigner 1701 will comprise a more flexible material; the adhesivematerial 1705 will comprise a material capable of bonding to a patient'stooth and the attachment; and the cover 1706, handle 1707, and couplingstructure 1704 will comprise materials that may be broken or removed byapplying a small amount of force with a hand or dental instrument. Othervariants, including the use of composite materials and other materialsas disclosed herein, will be apparent to one of ordinary skill in theart.

FIG. 17B illustrates a detailed view of a support 1703 of an attachmenttemplate, such as that illustrated in FIG. 17A. The support 1703 isillustrated in exaggerated format with a larger space than may be usedfor coupling structure 1704 in at least some cases, so that thestructure of the connection made by coupling structure 1704 betweenattachment 1702 and support 1703 may be more clearly seen. Asillustrated, coupling structure 1704 comprises one or more extensions1714, which hold the attachment 1702. After attaching attachment 1702 toa tooth, the extensions 1714 may be broken by applying a small amount offorce on the attachment template. The extensions 1714 may comprisestructures to facilitate breakage, such as a narrow cross sectionalprofile having a smaller cross section near the attachment and a largecross sectional profile having a larger cross section away from theattachment. Alternatively or in combination, the extensions may compriseadditional structures to facilitate removal such as a lower densitymaterial or voids, for example. The material of extensions 1714 maycomprise a material suitable to fracture such as a rigid material orbrittle material, for example. In some embodiments, the material of theextension 1714 may absorb infrared light or radio frequency radiation ata rate that is greater than one or more of the attachment 1702, thetemplate 1700, and the adhesive 1705. Absorbing infrared light or radiofrequency radiation may cause the extension to heat up and soften ormelt while the template and extension 1714 remain hard or solid,allowing the coupling structure 1704 to separate from the attachment1702. After freeing the extension from the coupling structure 1704, itmay be desirable to smooth the attachment surface to remove any jaggedor abrasive portions that may remain and cause discomfort to the patientor otherwise interfere with future interactions between the attachmentand appliance surfaces. FIG. 17B also illustrates a version of cover1706 comprising a loop structure as a handle, which may be used to moreeasily mate with a dental instrument.

In some embodiments, the material of the extension 1714 may bedissolvable in a liquid at a rate that is greater than the rate at oneor more of the attachment 1702, the template 1700, and the adhesive 1706dissolves. In some embodiments, the extensions 1714 may be configured tofracture or separate from the attachment when subjected to ultrasonicvibration.

In some embodiments, the template 1700 may define the shape of theattachment 1702. For example, the inner surface 1720 of the template1700 may be shaped to define an outer surface 1721 of the attachment1702. In such an embodiment the attachment 1702 may be formed directlyon the inner surface 1720 of the template 1700 such that the outersurface 1721 of the template 1700 takes on the shape of the innersurface of the attachment 1702. In some embodiments, the inner surfaceof the template 1700 may be coated with a release agent or non-stickcoating, such as Teflon, to facilitate separation of the attachment 1702from the template 1700 after attaching the attachment 1702 to a tooth.In some embodiments, the attachment 1702 may be formed from a UV curingmaterial, such that the template 1700 with the attachment 1702 can beplaced over a patient's tooth, the attachment 1702 can then be cured inplace in the template 1700 and on the patient's tooth, and then thetemplate 1700 may be removed from the patient's tooth, which theattachment 1702 remaining attached to the patient's tooth.

In order to accurately place the attachment on a patient's tooth, theattachment template can be fabricated as part of a larger appliancecomprising a plurality of tooth-receiving cavities, such as at least aportion of aligner 100 of FIG. 1, for example. The at least the portionof aligner 100 comprises a tooth-receiving alignment structure such asat least a portion of a tooth-receiving cavity so as to receive afeature of a tooth, for example. The attachment 1702 may be fabricatedwithin a receptacle of the aligner, such as receptacle 106. When thealigner 100 is placed upon a patient's teeth 102, the tooth-receivingcavities of the aligner receive the patient's teeth, holding the alignerin an orientation that may be used to precisely locate an attachment1702 on a patient's tooth. After bonding the attachment to the patient'stooth, the coupling structure 1704 may be separated from the attachment,and the aligner 100 removed, leaving the attachment 1702 attached to apatient's tooth, as shown in FIG. 1 as attachment 104. The attachmentcan be separated from the aligner 100 in many ways, for example with oneor more of breaking or separation of a weak bond between the attachmentand the at least the portion of the appliance. When placing a pluralityof attachments, the aligner 100 may comprise a plurality of receptacles106, each holding an attachment for one of a plurality of teeth 102. Insome cases, one or more tooth-receiving cavities may comprise aplurality of receptacles, allowing a plurality of attachments to beadhered to each of one or more teeth.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. Numerous differentcombinations of embodiments described herein are possible, and suchcombinations are considered part of the present disclosure. In addition,all features discussed in connection with any one embodiment herein canbe readily adapted for use in other embodiments herein. It is intendedthat the following claims define the scope of the invention and thatmethods and structures within the scope of these claims and theirequivalents be covered thereby.

What is claimed is:
 1. A method of fabricating an appliance, the methodcomprising: directly fabricating a dental appliance body including asupport formed in a tooth-receiving cavity, the tooth receiving cavityconfigured to receive a tooth; directly fabricating one or more couplingstructures to the support; and directly fabricating an attachment to thecoupling structure, the dental appliance body configured to align theattachment to a predetermined location on a tooth; wherein the one ormore coupling structures is configured to release the attachment withremoval of the dental appliance body from the tooth.
 2. The method ofclaim 1, wherein the tooth-receiving cavity, the support, and the one ormore coupling structures are directly fabricated together.
 3. The methodof claim 1, wherein the one or more coupling structures are configuredto break with removal of the alignment structure from the one or moreteeth.
 4. The method of claim 1, wherein the one or more couplingstructures are sized and shaped to hold the attachment.
 5. The method ofclaim 1, wherein the one or more coupling structures comprise aseparator sized and shaped to separate the attachment from the support.6. The method of claim 1, wherein the one or more coupling structurescomprises a recess formed in the support, the recess sized and shaped toseparate the attachment from the support.
 7. The method of claim 1,further comprising forming an adhesive on the one or more attachments.8. The method of claim 7, wherein the adhesive is directly fabricatedwith the dental appliance body.
 9. The method of claim 1, wherein theone or more coupling structures comprises one or more extensionsextending between the support and the attachment.
 10. The method ofclaim 9, wherein one or more extensions are formed with a material thatabsorbs infrared light at a rate greater than a rate of infraredabsorption of the dental appliance body.
 11. A method of planning adental treatment, the method comprising: determining a plurality ofstages for incremental repositioning of a patient's teeth, wherein theplurality of stages comprises an initial stage, an intermediate stage,and a final stage; determining, for at least one of the initial stage,the intermediate stage, and the final stage, the shape of acorresponding dental appliance body, wherein the dental appliance bodycomprises a support formed in a tooth-receiving cavity, one or morecoupling structures formed proximate to the support, and an attachmentformed proximate to the one or more coupling structures, wherein thedental appliance body is configured to align the attachment to apredetermined location on a tooth, and wherein the one or more couplingstructures is configured to release the attachment with removal of thedental appliance body from the tooth; and generating instructions fordirect fabrication of the dental appliance body.
 12. The method of claim11, wherein the tooth-receiving cavity, the support, and the one or morecoupling structures are directly fabricated together.
 13. The method ofclaim 11, wherein the one or more coupling structures are configured tobreak with removal of the alignment structure from the one or moreteeth.
 14. The method of claim 11, wherein the one or more couplingstructures are sized and shaped to hold the attachment.
 15. The methodof claim 11, wherein the one or more coupling structures comprise aseparator sized and shaped to separate the attachment from the support.16. The method of claim 11, wherein the one or more coupling structurescomprises a recess formed in the support, the recess sized and shaped toseparate the attachment from the support.
 17. The method of claim 11,wherein the instructions comprise forming an adhesive on the one or moreattachments.
 18. The method of claim 17, wherein the instructionscomprise directly fabricating the adhesive with the dental appliancebody.
 19. The method of claim 11, wherein the one or more couplingstructures comprises one or more extensions extending between thesupport and the attachment.
 20. The method of claim 19, wherein one ormore extensions are formed with a material that absorbs infrared lightat a rate greater than a rate of infrared absorption of the dentalappliance body.